Post-Prostatectomy Risk Stratification of Biochemical Recurrence Using Transfer Learning-Based Multi-Modal Artificial Intelligence

PURPOSE/OBJECTIVE(S)

For patients undergoing radical prostatectomy for prostate cancer (PCa), accurate risk stratification is essential to guide post-prostatectomy therapeutic decision making. Recently, there has been success in the use of multi-modal artificial intelligence models for men after prostate biopsy to aid in risk stratification. Herein, we trained and tested a TRansfer learning-based multi-modal Artificial InteLligence model (TRAIL) for biochemical recurrence (BCR) risk stratification following radical prostatectomy.

MATERIALS/METHODS

Patients contained within a prospective PCa registry at a single institution were utilized. Digital pathology slides from the diagnostic biopsies prior to radical prostatectomy for patients with clinically localized PCa were scanned at 20x resolution. Features were extracted for the TRAIL model from pathology slides via two transfer learning steps: (1) InceptionResNetv2 that first determines a heatmap of tumor areas, and (2) A ResNet18 that extracts representative features from the high tumor probability areas. Least Absolute Shrinkage and Selection Operator (LASSO) was used for feature selection from the pathology-extracted features. Finally, TRAIL combines the clinical and pathology-extracted features via a classification ensemble model based on weak tree learners to predict 2- and 5-year BCR defined as two consecutive serum PSA levels ≥0.2 ng/mL. TRAIL training was performed on 250 patients and was then locked and applied to the test set of 125 patients. Accuracy and the area under the curve (AUC) were calculated. Comparison to CAPRA-S and to clinical-only features were assessed.

RESULTS

A total of 818 digital whole pathology biopsy slides from 375 patients treated with subsequent radical prostatectomy were included. Surgical margins were positive in 29% of the patients, and 41% had extra-prostatic extension. The median follow-up was 48 months (Range: 1-132 months). The rates of 2-and 5-year BCR were 11% and 18% respectively. A total of 19 digital pathology-driven features were included in TRAIL. Clinical factors included age, ISUPG, Gleason score, PSA, pathological T and N stages, surgical margin involvement, and the presence of extra-prostatic extension. On the testing set, TRAIL achieved a 2-year BCR AUC of 0.76 and accuracy of 0.87, and was superior to CAPRA-S (AUC = 0.57) and clinical-only features (AUC 0.50, accuracy 0.14). For 5-year BCR, TRAIL achieved an AUC of 0.69 and accuracy of 0.78, and performed better than CAPRA-S (AUC = 0.58), and clinical only features (AUC = 0.50, accuracy = 0.23).

CONCLUSION

Through a combination of deep and ensemble learning, TRAIL incorporates clinical and histopathology features, enabling an improved BCR risk stratification post-prostatectomy when compared to the currently used clinicopathologic models. Future work with larger datasets with metastatic events is warranted to further optimize the model for clinical use.

Cross-Comparison Individual Patient Level Analysis of Three Gene Expression Signatures in Localized Prostate in over 50,000 Men

PURPOSE/OBJECTIVE(S)

Risk stratification guides the management of localized prostate cancer. Multiple commercial gene expression biomarkers have been developed to improve estimates of prognosis, however the 22-gene Decipher genomic classifier (22-GC) is the only test with level 1 evidence supporting its use per NCCN guidelines. It is unknown whether other commercial signatures, Oncotype (GPS) or Prolaris (CCP), are sufficiently correlated to negate the differences in evidence supporting these commercial tests. Herein, we aim to perform a cross-comparison of these signatures in a large cohort of patients diagnosed with localized prostate cancer.

MATERIALS/METHODS

Patients diagnosed with localized prostate cancer who underwent whole transcriptome gene expression microarray analysis on their primary tumor biopsy specimen were included. The 22-GC score was calculated by Veracyte using a commercially locked model. Individual genes in each of the GPS and CCP gene signatures were identified, and the gene weights in each signature were retrained for prediction of metastasis in a multi-institutional cohort of 1,574 men with long-term outcome data. This was performed to improve correlation performance of GPS and CCP given only the 22-GC was trained for prediction of metastasis. For each of the three signatures, both continuous and categorical scores were calculated. Linear regression and spearman correlations were calculated both on univariable and multivariable analyses adjusting for age, grade group, PSA, and T-stage.

RESULTS

A total of 50,881 patients were included (15,379 (30.2%) NCCN low-risk, 14,773 (29.0%) favorable intermediate-risk, 15,544 (30.5%) unfavorable intermediate-risk, and 5,185 (10.2%) high/very high-risk) with a median age of 68 years, and a median PSA of 6.2 ng/mL. On linear regression, the GPS model had poor goodness-of-fit to the 22-GC with an R2 of 0.36, as did the CCP model to the 22-GC with an R2 of 0.32. For CCP, the linear sum of the 31-genes was also tested but had inferior performance (R2 0.28) compared to the reoptimized CCP model. Results were similar on multivariable analysis adjusting for age, PSA, clinical stage and grade group. Spearman correlation between the continuous GPS model scores and the 22-GC was moderate at 0.59, as was the correlation between CCP model and the 22-GC of 0.54. CCP is a measure of proliferation, but in 22-GC high-risk patients, the majority (64.1%) of patients had low-average proliferation and only 35.9% had high proliferation, potentially explaining the lack of strong correlation.

CONCLUSION

There is minimal to moderate correlation between the 22-GC and GPS or CCP gene expression signatures tested. Therefore, these tests should not be viewed as interchangeable, and utilization should be based on the level of evidence supporting each gene expression biomarker.

Prostate Advanced Radiation Technologies Investigating Quality of Life (PARTIQoL): A Phase III Randomized Clinical Trial of Proton Therapy vs. IMRT for Low or Intermediate Risk Prostate Cancer

PURPOSE/OBJECTIVE(S)

Prostate cancer is the most common non-cutaneous cancer diagnosed among men in the United States, and the majority of patients are diagnosed with localized disease. Men with localized prostate cancer have several treatment options including external beam radiotherapy with either photons or protons. Proton beam therapy (PBT) has certain dosimetric advantages and the potential to reduce treatment-associated morbidity and improve oncologic outcomes, but current PBT is significantly more costly than intensity-modulated radiotherapy (IMRT). The PARTIQoL trial (NCT01617161) is the first multicenter phase 3 randomized trial comparing protons to photons in the treatment of localized prostate cancer.

MATERIALS/METHODS

Patients with low or intermediate risk prostate cancer (Stage T1c-T2c, PSA < 20, Gleason score ≤ 7) are randomized to receive either PBT or IMRT, with targeted recruitment efforts for minority populations. A companion registry study has concurrently enrolled patients who declined randomization or whose insurance denied coverage for PBT. Patients are stratified by clinical site, age, use of rectal spacer, and fractionation schedule (conventional fractionation: 79.2 Gy in 44 fractions vs moderate hypofractionation: 70.0 Gy in 28 fractions). Participants are followed longitudinally to assess patient-reported outcomes (PROs) of bowel, urinary, and erectile function for 60 months after completion of radiotherapy (with an option for additional follow up through 10 years). Participants may also participate in correlative studies, including serial CT imaging during treatment and analyses of biopsy tissue, blood and urine specimens. The primary objective is to compare PROs of bowel function using the EPIC score at 24 months following completion of radiation. Secondary objectives are to assess treatment-related differences in urinary and erectile functions, adverse events, efficacy endpoints (biochemical control, metastasis-free survival, disease-specific survival, and overall survival), health state utilities, perceptions of care, late effects, cost-effectiveness, association between radiotherapy dose distribution and PROs, and to identify biomarkers of radiation response and toxicity.

RESULTS

The randomized trial has completed accrual, with 450 patients enrolled at 27 sites between June 2012 and November 2021. 20.3% of patients enrolled are non-white. Accrual on the companion registry is active, with 354 patients enrolled as of February 2023.

CONCLUSION

Follow-up for the primary endpoint on the randomized trial will be reached in 2024. The PARTIQoL randomized clinical trial will rigorously assess the clinical benefits of PBT relative to IMRT and results will inform decision making by patients, providers, policymakers, and payers.

Projected Lifetime Earnings of a Radiation Oncologist

PURPOSE/OBJECTIVE(S)

The estimated lifetime earnings of a radiation oncologist depend on many choices and have not been calculated. The objective of this work is to project the year-by-year and cumulative lifetime earnings of a US-based radiation oncologist based on various career pathways.

MATERIALS/METHODS

We modeled lifetime earnings based on undergraduate training (reference: assumes starting at age 18, tuition/loans of $40,000 x 4 years), MD/DO (reference: assumes tuition/loans of $55,000 x 4 years, 8% interest) vs MD/PhD program (assumes no tuition, $30,000 yearly stipend x 8 years), gap year(s), fellowship, employment paths (academic, private practice, hospital employed, physician scientist with NIH salary cap), adjustable salary during employment (based on 2016-2018 AAMC and MGMA; e.g., promotion for academic track, partnership for private practice), adjustable state and federal income taxes, loan repayment options (e.g., out of pocket, NIH loan repayment program [LRP], public service loan forgiveness [PSLF]). The primary outcome was cumulative lifetime earnings, and additional analyses were conducted based on changes in career paths. We created a web-based application to simulate the various choices using R Shiny: https://physician-earnings.shinyapps.io/rshiny/.

RESULTS

For an academic radiation oncologist, assuming MD/DO degree, national average of $220,000 in loans at medical school graduation, 5% state income tax, no gap years, pursuing PSLF, starting as assistant professor, 7 year promotion until associate professor, and 7 subsequent year promotion to full professor, and retirement age of 65, the post-tax median lifetime earnings are $9,610,675 (IQR $8,097,433 - $10,885,824), with $5,242,653 federal + state taxes. With the private practice setting, the median lifetime earnings are $11,383,781 (IQR $9,875,040 - $13,325,316). As a hospital employee, the median lifetime earnings are $8,834,886 (IQR $8,127,132 - $10,166,145). As an NIH-salary capped physician scientist, the median lifetime earnings are $4,678,668 (IQR not provided, given one set cap). Using the academic track as the reference group, the median lifetime earnings would change as follows: $9,333,434 (IQR $7,876,310 - $10,572,388) for those who pursue one paid undergraduate gap year; $9,125,590 (IQR $7,822,115 - $10,274,801) for those who pursue MD/PhD programs; $10,365,300 (IQR $8,725,954 - $11,746,712) for those with 0% state income tax during practice; and $9,565,364 (IQR $7,875,284 - $10,802,830) for those who repay their loans out of pocket at 50% of their attending salary. PSLF and NIH LRP allow one to cross a net worth of $0 by their mid-30s; pursuit of fellowship, starting as an instructor in academics, salary in bottom quartile %, paying loans out of pocket, and gap years all delay this landmark by 1-4 years. NIH-salary capped positions have the largest negative impact on lifetime earnings, by > $5,000,000.

CONCLUSION

We created a model to estimate lifetime earnings of a radiation oncologist in the US.

Quantifying the Impact of Research Productivity on Salary in Academic Radiation Oncology

PURPOSE/OBJECTIVE(S)

Academic physicians typically do not receive a salary based on individual publications; however, publications are necessary for promotion, and the impact of publication productivity among ranks on salary is unknown. The objective of this was to evaluate salary changes associated with publication productivity among academic radiation oncologists.

MATERIALS/METHODS

Radiation oncologist faculty-level academic productivity data were obtained, including the h-index, m-index, number of papers, and number of citations, based on prior work (Holliday et al, 2014). The AAMC and MGMA Provider Compensation Data from 2017 provided percentile-level salaries. The delta in salary was calculated for each delta in rank the publication metrics among ranks. The primary outcome was delta in salary per delta in h-index; additional calculations were performed for delta in m-index and delta in publications.

RESULTS

A total of 986 radiation oncologists were included. For assistant professor, median salary was $367,000, average h-index 6.8, m-index 0.68, 15.7 publications. For associate professor, median salary was $452,000, average h-index 14, m-index 0.87, 41.8 publications. For full professor, median salary was $520,000, average h-index 31.3, m-index 1.33, 118.7 publications. For chair (not mutually exclusive from full professor), median salary was $720,000, average h-index 34.8, m-index 1.36, 146.8 publications. The delta in salary per delta in rank and the associated changes in h-index, m-index, and publications are shown in Table 1. The average change in salary from assistant to associate professor is $11,805.56 / h-index, $447,368.42 / m-index, and $3,256.70 / publication; for associate to full it is $3,930.64 / h-index, $147,826.09 / m-index, and $884.27 / publication; and for full to chair it is $57,142.86 / h-index, and $7,117.44 / publication.

CONCLUSION

This work provides the average change in salary among academic ranks based on changes in research publication productivity. Our present analysis is unable to assess causality of this association, and many unaccounted confounders may affect this relationship. Further work in this area may include evaluation of demographic factors that have demonstrated rank and salary disparities in radiation oncology, such as gender.

Validation of a Genomic Classifier in the NRG Oncology/RTOG 0521 Phase III Trial of Docetaxel with Androgen Suppression and Radiotherapy for Localized High-Risk Prostate Cancer

PURPOSE/OBJECTIVE(S)

Decipher is a prognostic genomic classifier (GC) validated in several prospective NRG Oncology Phase III trials. Herein, we validate the GC in pre-treatment biopsy samples for risk stratification in a cohort of high-risk men treated with definitive radiotherapy and androgen suppression with or without docetaxel chemotherapy.

MATERIALS/METHODS

As per a pre-specified and approved NCI analysis plan (Navigator #1061), we obtained available formalin-fixed paraffin-embedded tissue from biopsy specimens from the NRG biobank from patients enrolled on the NRG/RTOG 0521 randomized phase III trial. After central review, the highest-grade tumors were profiled on clinical-grade whole-transcriptome arrays (Veracyte, San Diego, CA) and GC scores were obtained. Pre-specified categorical GC scores, adjusted for archival tissue analysis, were used to define higher (>0.46) and lower (≤0.46) risk groups. The primary objective was to validate the independent prognostic ability of GC for metastasis-free survival (MFS) with Cox multivariable analyses (MVA).

RESULTS

Samples were obtained from 283 consented, evaluable patients with tissue (50% of trial) yielding 183 (65%) GC scores that passed quality metrics, 91 from control and 92 from the interventional arm. Median age was 66 years, median PSA was 19.3 ng/uL (IQR: 8.1-41.4), 81% had clinical stage ≥T2 and 80% had Gleason score ≥8 (47% ≥9). Median GC score was 0.55 (IQR: 0.38-0.78) and overall the arms were balanced for key covariates. With a median follow-up of 9.9 years (IQR: 9.3, 10.7), 67 MFS events including 34 distant metastases (DM) were observed. On MVA, only the GC (per 0.1 unit) was independently associated with MFS (HR 1.12, 95% CI 1.01-1.25) as well as DM (sHR 1.22, 95% CI 1.06-1.41), whereas the 4 pre-defined trial risk groups used for stratification (based on Gleason score, T-stage and PSA), randomization and patient age were not. For categorical GC, on MVA, higher-risk GC patients (65%) had worse DM (sHR 2.82, 95% CI 1.1-7.3) compared to those with lower GC. Cumulative incidence of DM at 10-years was 27% for higher GC vs 9% (95% CI 7-18%) for lower GC. No biomarker-by-treatment interaction with GC and the addition of docetaxel was detected.

CONCLUSION

In pre-treatment biopsy samples from a randomized Phase 3 trial cohort, GC demonstrated its ability to further risk stratify clinically high-risk men demonstrating an independent association of GC score with DM and MFS. High-risk prostate cancer is a heterogeneous disease state and GC can improve risk stratification to help personalize shared decision-making. NRG-GU009/PREDICT-RT (NCT04513717) aims to determine the optimal therapy based on GC score for high-risk prostate cancer.

Individual Patient Data Analysis of 17 Randomized Trials vs. Real-World Data for Men with Localized Prostate Cancer Receiving Radiotherapy

PURPOSE/OBJECTIVE(S)

Prior work has demonstrated poor correlation between the results of randomized controlled trials (RCTs) and real-world evidence (RWD). However, patients enrolled in RCTs are often considered to poorly represent the real-world population. Herein, we utilize multiple large data repositories to determine differences in baseline characteristics and long-term outcomes between patients enrolled in RCTs and RWD that received radiotherapy for localized prostate cancer.

MATERIALS/METHODS

Meta-Analysis of Randomized trials in Cancer of the Prostate (MARCAP) Consortium was leveraged, and 17 phase III randomized trials were included. RWD were accessed through the Staging Collaboration for Cancer of the Prostate (STAR-CAP) cohort, a cohort that is comprised of >60 centers across the United States and Europe. Additionally, RWD was assessed via the Surveillance, Epidemiology, and End Results (SEER) database. MARCAP and STAR-CAP both contain outcomes for distant metastasis (DM), metastasis-free survival (MFS), prostate cancer-specific mortality (PCSM), and overall survival (OS). SEER only contains PCSM and OS. Wilcoxon signed-rank test and chi-square test were used to compare continuous and categorical variables, respectively. Inverse probability of treatment weighting (IPTW) analysis was conducted, balancing for age, PSA, Gleason score, T stage, and treatment year in the three cohorts. Cox and Fine-Gray regression models were used to compare disease outcomes between RCTs vs. RWD.

RESULTS

Data from 10,666 patients from RCTs, 6,530 patients in STAR-CAP, and 117,586 patients in SEER were included. SEER patients were slightly younger (p<0.001, median age 68 (IQR 62-73) than those in RCTs (70, IQR 65-74) and in STAR-CAP (70, IQR 64-74). 10-year OS in RCTs was 65.4%, STAR-CAP 70.2%, SEER 64.1%. OS was superior in STAR-CAP (RCTs as reference; HR 0.91, 95% CI 0.85-0.96, p<0.0001), but there was no significant difference between SEER and RCTs (HR 0.96, 95% CI 0.91-1.02, p = 0.22). 10-year PCSM cumulative incidence was 7.4% in RCTs, 8.1% in STAR-CAP, and 11.0% in SEER. There was no significant difference in PCSM between STAR-CAP RWD and RCTs (HR 0.88, 95% CI 0.78-1.01, p = 0.08), whereas PCSM was worse in SEER than RCTs (HR 1.37, 95% CI 1.21-1.55, p<0.0001). There was no significant difference in DM between STAR-CAP RWD and RCTs (HR 0.93, 95% CI 0.83-1.04, p = 0.2).

CONCLUSION

While baseline differences exist in patients enrolled on localized prostate cancer RCTs and real-world datasets, there were small if any significant relative differences in oncologic outcomes. This provides reassurance that RCT results are generally applicable to patients in routine practice.

A Systematic Review and Network Meta-Analysis Assessing the Impact of Adding First Generation Non-Steroidal Anti-Androgens (NSAA) to LHRH Agonists (LHRHa) in Men Receiving Radiotherapy for Localized Prostate Cancer

PURPOSE/OBJECTIVE(S)

Randomized clinical trials consistently demonstrate that the addition of androgen deprivation therapy (ADT) to prostate radiation therapy improves overall survival (OS). However, there is substantial heterogeneity regarding the type of ADT: LHRHa alone, first generation NSAA alone (e.g., bicalutamide) or combination androgen blockade (CAB) with NSAA and LHRHa. There are no published randomized trials in localized disease that specifically compare the efficacy of NSAA to LHRHa, nor the utility of CAB over monotherapy ADT. We herein performed a systematic review and network meta-analysis to assess the impact of NSAA in relation to LHRHa in men receiving radiotherapy for localized prostate cancer.

MATERIALS/METHODS

We performed a systematic literature search in PubMed to identify clinical trials of patients with localized prostate cancer for which ADT duration was the primary randomization variable. Both definitive and salvage radiation trials were included. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated from data extracted from published survival curves. A network meta-analysis was performed to compare OS by ADT regimens. We defined NSAA toxicity as early discontinuation of any ADT agent due to side effects given the inconsistent reporting of specific related toxicity. A meta-regression was performed to assess association with NSAA toxicity, adjusted for study year, patient age, T stage, Gleason score and total ADT duration. NSAA duration was assessed as a continuous variable.

RESULTS

Of the 11 trials (8,169 patients) with OS data, the median duration of any ADT was 3 months (range 0-36 months) and the median duration of NSAA specifically was 3.5 months (range 0-24 months). There was no significant difference in OS between those treated with LHRHa (n = 369) vs. CAB (n = 4,792; HR 1.10, 95% CI 0.78-1.55). Among those receiving CAB, increased NSAA duration did not improve OS (versus 0 months; 1-6 months HR 1.41, 95% CI 0.94-2.13; 7-12 months HR 1.43, 95% CI 0.87-2.34) when controlling for total ADT duration. Of the 19 trials (15,067 patients) with toxicity data, patients on NSAA (n = 503) appeared more likely to discontinue treatment early compared to those receiving LHRHa (n = 902), though this was not statistically significant (odds ratio [OR] 4.20, 95% CI 0.16-109.19). A longer duration of NSAA did not adversely affect ADT compliance. Patients were more likely to discontinue ADT prematurely, regardless of type, if the planned duration was longer (OR 1.08, 95% CI 1.07-1.09).

CONCLUSION

We did not detect an overall survival benefit to adding NSAA to LHRHa, and NSAA appeared less well tolerated than LHRHa in men receiving radiation therapy for localized prostate cancer. These data suggest that providers should consider LHRHa without the addition of a NSAA as optimal when clinically appropriate.

Transcriptomic Analysis to Uncover the Mechanism of Radiosensitization of AR-Positive Triple Negative Breast Cancers with AR Inhibition

PURPOSE/OBJECTIVE(S)

The androgen receptor (AR) has been shown to drive tumor growth in triple negative breast cancers (TNBC), and previous work demonstrated AR inhibition as a strategy for radiosensitization in AR-positive (AR+) TNBC. Despite its role in radioresistance, the mechanistic role of AR in response to radiation therapy (RT) remains unknown, as does the benefit of 2nd generation anti-androgens in this context. We hypothesized that all 2nd generation anti-AR therapy would radiosensitize similarly and that canonical AR transcriptional function was responsible for radioresistance in these models.

MATERIALS/METHODS

Radiosensitization was assessed using 2nd generation AR antagonists (apalutamide, enzalutamide, and darolutamide) using clonogenic survival assays in MDA-MB-453, SUM185, MFM-223, and MDA-MB-231 cells at 2-6Gy. Cellular fractionation experiments were performed and quantitated to determine the location of the AR protein in cells treated with AR agonists +/- RT. RNA Seq was performed and transcriptomic approaches were used (Advaita iPathway analysis) to investigate AR-mediated effects in response to RT.

RESULTS

Inhibition with the 2nd generation anti-androgens enzalutamide and apalutamide is sufficient to radiosensitize AR+ TNBC models (rER: 1.34-1.41); while darolutamide had no effect on radiosensitivity (rER: 0.96-1.11). Additionally, TNBC cells with low AR expression were not radiosensitized by AR inhibition with any drug (rER: 0.96-1.03). While stimulation with the synthetic androgen methyltrienolone R1881 is sufficient to induce nuclear translocation of AR in AR+ TNBC cells, AR inhibition with enzalutamide, apalutamide, or darolutamide blocked AR nuclear translocation under growth conditions with charcoal stripped serum or fetal bovine serum. When cells are treated with R1881+RT, nuclear translocation of AR was induced at similar or greater levels compared to R1881 alone in AR+ TNBC cells. Combination treatment of RT with enzalutamide in the presence of hormones reduced nuclear localization of AR (32-39% reduction) compared to RT alone. RNA-sequencing after RT identified transcriptional changes potentially regulated by AR+RT, including changes in the NHEJ pathway genes. Additionally, pathway analyses in these models demonstrated changes in the MAPK/ERK signaling pathway, among others, that may regulate RT resistance in AR+ TNBC models.

CONCLUSION

Most 2nd generation anti-androgens confer radiosensitization in AR+ TNBC models with cellular localization changes of AR noted after RT. The known structural differences amongst 2nd generation anti-androgens may account for differences in radiosensitization noted. Furthermore, AR-mediated radioresistance may be due, at least in part, to downstream MAPK/ERK signaling. This work builds on the mechanistic understanding of AR-mediated radioresistance in AR+ TNBC and may expose vulnerabilities to overcome resistance to combination treatment with AR inhibition and RT.

FORMULA-509: A Multicenter Randomized Trial of Post-Operative Salvage Radiotherapy (SRT) and 6 Months of GnRH Agonist with Either Bicalutamide or Abiraterone Acetate/Prednisone (AAP) and Apalutamide (Apa) Post-Radical Prostatectomy (RP)

PURPOSE/OBJECTIVE(S)

FORMULA-509 was designed to evaluate whether adding six months of AAP and Apa to a GnRH Agonist could improve outcomes compared to six months of bicalutamide plus GnRH Agonist for patients with unfavorable features receiving SRT for a detectable PSA post-RP.

MATERIALS/METHODS

FORMULA-509 is an investigator-initiated, multi-center, open-label, randomized trial. Patients had PSA ≥0.1 post-RP and one or more unfavorable features (Gleason 8-10, PSA >0.5, pT3/T4, pN1 or radiographic N1, PSA doubling time <10 months, negative margins, persistent PSA, gross local/regional disease, or Decipher High Risk). All patients received SRT plus 6 months of GnRH agonist and randomization was to concurrent bicalutamide 50 mg or AAP 1000 mg/5 mg + Apa 240 mg QD. Radiation to pelvic nodes was required for pN1 and optional for pN0. The primary endpoint was PSA progression-free survival (PFS) and secondary endpoint was metastasis-free survival (MFS) determined by conventional imaging. The study was powered to detect a HR of 0.50 for PFS and a HR of 0.30 for MFS, each with 80% power and one-sided type I error of 0.05. Stratification was by PSA at study entry (>0.5 vs.≤0.5) and pN0 vs pN1. Analyses within these subgroups were pre-planned and utilized two-sided p-values.

RESULTS

Three hundred forty-five participants (332 evaluable) from 9 sites were randomized from 11/24/2017 to 3/25/2020 (172 bicalutamide, 173 AAP/Apa). Median follow-up was 34 (6-53) months; 29% were pN1 and 31% had PSA >0.5 ng/mL. The HR for PFS was 0.71 (90% CI 0.49-1.03), stratified one-sided log-rank p = 0.06 (3-year PFS was 68.5% bicalutamide vs 74.9% AAP/Apa). The HR for MFS was 0.57 (90% CI 0.33-1.01), stratified one-sided log rank p = 0.05 (3-year MFS was 87.2% bicalutamide vs 90.6% AAP/Apa). In a pre-planned analysis by stratification factors, AAP/Apa was significantly superior for patients with PSA >0.5 for PFS [HR 0.50, (95% CI 0.27-0.95), p = 0.03 (2-sided); 3-year PFS 46.8% bicalutamide vs. 67.2% AAP/Apa] and for MFS [HR 0.32 (95% CI 0.13-0.84), p = 0.02 (2-sided); 3-year MFS 66.1% bicalutamide vs. 84.3% AAP/Apa.] No statistically significant benefit was detected in pre-planned analyses of stratification subgroups defined by PSA≤0.5, pN0, or pN1. Adverse events were consistent with the known safety profiles of the agents being studied, with more rash and hypertension in the AAP/Apa arm.

CONCLUSION

Although this primary analysis did not meet the pre-specified threshold for statistical significance, it does strongly suggest that the addition of AAP/Apa instead of bicalutamide to SRT+6 months of GnRH Agonist may improve PFS and MFS, particularly in the subgroup of patients with PSA>0.5 where a pre-planned subgroup analysis by stratification factors observed a statistically significant benefit for both PFS and MFS. (NCT03141671).

Impact of Prior Radiation Therapy on Bone Mineral Density Change Over Time: Secondary Analysis of the Control Arm of a Phase III Randomized Trial

PURPOSE/OBJECTIVE(S)

Retrospective studies have demonstrated that pelvic radiation therapy (RT) can lead to decreased bone mineral density (BMD) and increased risk of fracture. This is more relevant for men with prostate cancer (PCa) who often receive androgen deprivation therapy (ADT) in conjunction with RT. We performed a post-hoc secondary analysis of publicly available data of the control arm of a phase III randomized controlled study (NCT00089674) to determine if history of prior pelvic RT affects change in BMD over time in non-metastatic PCa patients treated with ADT.

MATERIALS/METHODS

In this study, PCa patients with age ≥70 years or <70 years with low BMD (T-score <-1) or history of osteoporotic fracture, on ADT for at least 12 months were randomized to receive densoumab vs. placebo every 6 months for 3 years. Additionally, all patients received daily vitamin D and calcium supplementation. Randomization was stratified by duration of prior ADT (≤6 months vs >6 months) and age (<70 vs ≥70 years). BMD was measured at baseline, and at months 1, 3, 6, 12, 24, and 36 with blind reading by central reviewer. To model the effect of prior pelvic RT on dynamic change in BMD in the hip, lumbar spine, and femoral neck, we applied separate multivariate linear mixed effect models for each site. Age, ECOG performance score, history and number of prior fractures, smoking history, and years from initial cancer diagnosis were included as fixed covariates while patients were included as random intercepts.

RESULTS

Among 734 patients who were randomized to the control arm, 563 participants with baseline and at least one post baseline assessment of BMD were eligible for this analysis. Overall, 34.4% (n = 194) received prior RT. We did not find any significant association of dynamic change in BMD with receipt of prior pelvic RT for left femoral neck (p = 0.7), total hip (p = 0.8), and lumbar spine (p = 0.5), respectively. At 36 months, there was no significant association of prior RT with percent change in BMD in femoral neck (odds ratio [OR]: 0.85; 95% confidence interval [CI]: 0.30-2.41), total hip (OR: 0.96; 95% CI: 0.43-2.15), and lumbar spine (OR: 2.01; 95% CI: 0.63-6.45). However, note should be made of the opposite direction of association of prior RT with percent BMD change at 36 months for femoral neck and hip versus lumbar spine.

CONCLUSION

In this exploratory analysis of the control arm of a phase III randomized trial, we did not find sufficient evidence of an association between prior pelvic RT and dynamic changes in BMD in femoral neck, hip, and lumbar spine over time in men with non-metastatic PCa and low BMD at baseline. This analysis should be interpreted cautiously considering its post-hoc nature with likely inadequate power, the possibility of selection bias, lack of information on receipt of prior ADT, and missing data in longitudinal assessments.

Association of Prostate Specific Antigen Kinetics after Testosterone Recovery with Subsequent Recurrence: Secondary Analysis of a Phase III Randomized Controlled Trial

PURPOSE/OBJECTIVE(S)

The combination of short-term androgen deprivation therapy (ST-ADT) with prostate radiotherapy (RT) is a standard of care for patients with localized prostate cancer (LPCa). After cessation of ST-ADT, it takes about 8 to 10 months for the testosterone (T) to recover to supracastrate levels, which could drive changes in PSA kinetics. It largely remains unknown whether early changes in PSA kinetics after T recovery could predict for subsequent biochemical relapse.

MATERIALS/METHODS

We performed a secondary analysis of a phase III randomized controlled trial in which patients with newly diagnosed LPCa with Gleason score £7, clinical stage T1b to T3a, and PSA <30 ng/mL were randomly allocated to neoadjuvant and concurrent ADT for 6 months starting 4 months before prostate RT (76 Gy in 38 fractions over 7.5 weeks) or concurrent and adjuvant ADT for 6 months starting simultaneously with prostate RT. Clinical assessment and laboratory investigations were repeated 1 month after completion of ADT, every 4 months for the first 2 years, every 6 months for the next 3 years, and annually thereafter. We calculated the PSA doubling time (PSADT) based on PSA values up to 18 months after recovery of T to a supracastrate level (>50 ng/dL). Patients with ³3 PSA measurements after T recovery to supracastrate level were included in this analysis. Fine and Gray cumulative incidence of biochemical recurrence (BCR) was calculated in patients with PSADT at or above median versus below median. Deaths were considered as competing events. All endpoints were calculated from the time of T recovery to supracastrate level. Subdistribution hazard ratios (sHR) with 95% confidence intervals (CI) were estimated for association of PSADT with relative incidence of recurrence using competing risk regression after adjusting for tumor stage, pre-treatment PSA, Gleason score, treatment regimen, and age at randomization.

RESULTS

Overall, 311 patients were eligible for this analysis. Median PSADT was 8 months. Cumulative incidence of BCR at 10 years was 31.0% and 20.7% in patients with PSADT <8 months and ³8 months, respectively. Longer PSADT was associated with a significantly lower risk of cumulative incidence of BCR (sHR for PSADT as a continuous variable 0.43, 95% CI: 0.28-0.66; sHR for PSADT ³8 months 0.54, 95% CI: 0.30-0.99). After adjustment for time to recovery of T to supracastrate level in addition to the aforementioned variables, longer PSADT (³8 months) was associated with lower risk of cumulative incidence of BCR (sHR: 0.53, 95% CI: 0.27-1.01).

CONCLUSION

These findings suggest that early PSA kinetics within 18 months of recovery of T to a supracastrate level predict for subsequent biochemical failure. Taking account of early changes in PSA after testosterone recovery may allow for recognition of potential failures earlier in the disease course and thereby permit greater personalization of management decisions.

Patient-Reported Urinary and Bowel Quality of Life Outcomes Following External Beam Radiotherapy with or without High-Dose-Rate Brachytherapy Boost: Post-Hoc Analyses of TROG 03.04 (RADAR)

PURPOSE/OBJECTIVE(S)

One of the concerns with combining external beam radiotherapy (EBRT) with a high dose rate brachytherapy boost (HDRBT) for prostate cancer is increased toxicity. We aimed to evaluate long-term urinary and bowel quality of life (QoL) outcomes following EBRT vs EBRT + HDRBT using data from the TROG 03.04 trial.

MATERIALS/METHODS

Men who had dose-escalated EBRT (74 Gy) or EBRT (46 Gy) + HDRBT (19.5 Gy in 3 fractions) were included in this exploratory analysis. QoL outcomes were prospectively collected using the EORTC-QLQ-PR25 at baseline, end of radiotherapy, 12, 18, 24, 36, 60 months, and annually up to 10 years. QoL score was normalized to 0-100 with higher scores representing worse symptom burden. Minimal clinically important differences (MCIDs) were defined as differences in the respective QoL scores ≥0.5 standard deviations of the baseline QoL score. Mixed models for repeated measures were used to evaluate longitudinal changes in the QoL score between EBRT and EBRT + HDRBT arms. Logistic regression was used to evaluate differences in proportion of men with 2xMCID between EBRT and EBRT + HDRBT arms at each time point. Age, baseline QoL score, ECOG performance status, and duration of androgen deprivation therapy use (6 vs. 18 months) were adjusted for in all analyses.

RESULTS

Four hundred ninety-seven men were included in this study: 260 (52%) had EBRT and 237 (48%) had EBRT + HDRBT. The median baseline urinary QoL scores were 12.5 (IQR 4.2-19.0) and 8.3 (IQR 4.2-20.8) for men in EBRT and EBRT + HDRBT arms respectively (P = 0.5). Within the first 24 months, men in the EBRT + HDRBT arm had a slower rate of urinary QoL score resolution compared to men in the EBRT arm (P<0.001). At 12, 18, 24, and 36 months, men who had EBRT + HDRBT were 2.4 times (95% CI = 1.4-4.0; P<0.001), 3.1 times (95% CI = 1.8-5.1; P<0.001), 2.8 times (95% CI = 1.7-4.7; P<0.001), and 2.5 times (95% CI = 1.4-4.5; P = 0.002) more likely to have 2xMCID in urinary QoL scores compared to men who had EBRT alone. Beyond 24 months, there were no significant differences in the rate of urinary QoL score resolution between arms, and beyond 36 months there were no significant differences in the proportion with 2xMCID between arms. The median baseline bowel QoL score was 0 in both arms. There were no differences in the rate of bowel QoL score recovery over time between arms. Men who had EBRT + HDRBT were less likely to have 2xMCID in bowel QoL score in the immediate post-radiotherapy period (OR = 0.66; 95% CI = 0.45-0.97; P = 0.03) and at 60 months (OR = 0.51; 95% CI = 0.33-0.80; P = 0.003) compared to men who had EBRT.

CONCLUSION

EBRT + HDRBT is associated with disturbances in urinary QoL that are of greater magnitude compared to EBRT alone within the first 36 months of treatment, but the differences resolved after 36 months. EBRT + HDRBT is associated with less disturbances in bowel QoL immediately after treatment and at 60 months compared to EBRT alone.

Fracture Risk Following Lumbosacral Spine SBRT in Patients Having Received Previous Whole Pelvis Radiation Therapy

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) for metastatic spinal disease provides local control with palliative effects1. Previous studies have demonstrated a posttreatment fracture rate range of roughly 5.7-39%2, with 14-17% the most commonly cited fracture risk range. However, the rate of spine fracture after lumbosacral SBRT in patients having received prior pelvic radiation therapy (RT) is unclear. The purpose of this study is to investigate the incidence of fracture in patients receiving lumbosacral spine SBRT following previous whole pelvic RT.

MATERIALS/METHODS

This study was a single institution retrospective chart review. All lumbar and sacral spine SBRT cases over a 5-year period (from January 2018 through September 2022) with at least three months of post-treatment follow-up were identified. Patients having previously received pelvic RT were assessed; the development of a vertebral fracture was recorded as was the time to fracture and potential intervention (if any).

RESULTS

A total of 35 lumbosacral spine SBRT cases were identified. Of those eight (23%) previously received whole pelvic RT, ranging from 20-70 Gy/5-35 fractions. Of the lumbosacral spine SBRT patients having received prior pelvic RT, two (25%) developed a fracture post-treatment. The average time to fracture was 7.5 months. Both fractures were treated with conservative management; neither required vertebroplasty/kyphoplasty or operative stabilization. The mean dose per SBRT fraction for patients who suffered a fracture (8.5 Gy) did not significantly differ from that for patients who did not suffer a fracture (9 Gy).

CONCLUSION

In the first examination of lumbosacral fracture risk following SBRT to patients having received previous pelvic RT, the fracture rate in this patient population was 25%. Noteworthy is that the SBRT dose per fraction did not differ between patients having suffered a fracture versus those without fracture. These findings indicate that patients having received previous whole pelvis RT should be counseled on the potential increased risk of fracture; however, there is no evidence that decreasing SBRT dose per fraction reduces the likelihood of fracture in this patient population. This increased fracture rate is of concern, and further investigation in larger studies to identify potential risk factors for vertebral fracture such as systemic therapy, age and gender is warranted.

A Meta-analysis of the Efficacy and Safety of Stereotactic Arrhythmia Radioablation (STAR) in Patients with Refractory Ventricular Tachycardia

AIMS

Reports of stereotactic arrhythmia radioablation (STAR) in patients with refractory ventricular tachycardia after catheter ablation are limited to small series. Here, we carried out a systematic review and meta-analysis of studies to better determine the efficacy and toxicity of STAR for ventricular tachycardia.

MATERIALS AND METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) and the Meta-analyses Of Observational Studies in Epidemiology (MOOSE) guidelines, eligible studies were identified on Medline, Embase, Cochrane Library and the proceedings of annual meetings to 10 February 2023. Efficacy was defined as a ventricular tachycardia burden reduction >70% at 6 months; safety was defined as <10% of any grade ≥3 toxicity.

RESULTS

Seven observational studies with a total of 61 patients treated were included. At 6 months, the ventricular tachycardia burden reduction was 92% (95% confidence interval 85-100%) and use of fewer than two anti-arrhythmic drugs was seen in 85% (95% confidence interval 50-100). Six months after STAR, an 86% reduction (95% confidence interval 80-93) in the number of implantable cardioverter-defibrillator shocks was observed. The rates for improved, unchanged and decreased cardiac ejection fraction were 10%, 84% and 6%, respectively. Overall survival at 6 and 12 months was 89% (95% confidence interval 81-97) and 82% (95% confidence interval 65-98). The cardiac-specific survival at 6 months was 87%. Late grade 3 toxicity occurred in 2% (95% confidence interval 0-5%) with no grade 4-5 toxicity.

CONCLUSION

STAR demonstrated both satisfactory efficacy and safety for the management of refractory ventricular tachycardia and was also associated with a significant decline in anti-arrhythmic drugs consumption. These findings support the continued development of STAR as a treatment option.

Radiographic progression-free survival (rPFS) and time to radiographic progression (TTrP) as surrogate endpoints in docetaxel-naïve metastatic castrate resistant prostate cancer (mCRPC): A pooled analysis of COU-AA-302 and ACIS

136

Background: rPFS is often used as an intermediate clinical endpoint (ICE) for overall survival (OS) in randomized trials in mCRPC. However, the current literature shows conflicting results on the surrogacy of rPFS for OS. Moreover, it remains unknown if TTrP, which does not consider death as an event, is an ICE for OS. We performed a combined analysis of COU-AA-302 and ACIS to determine if TTrP and rPFS can be used as ICE. Methods: In COU trial, docetaxel-naïve mCRPC patients were randomized to abiraterone (abi) versus placebo. In ACIS, a similar patient population was randomized to abi alone or abi with apalutamide (abi+apa). We applied weighted Cox regression models to evaluate the effect of treatment on TTrP and OS and used landmark analyses to determine the if the treatment effect on OS is mediated by that on radiographic progression. We estimated a semiparametric Spearman correlation between the ICE and OS at the patient level. We determined the trial level correlation of treatment effect on the ICE and OS in the 2 trials where each of them was subdivided into 9 pseudo-trial centers and then calculating the adjusted R2 between center level estimates of treatment effect for ICE and OS. The procedure of creating pseudo-trial centers was repeated 500 times and the presented R2 is the average across 500 repetitions after excluding those with negative association. Results: Overall, 2016 patients were eligible for this study – 1053 from COU and 963 from ACIS. Abi was associated with superior TTrP (HR 0.55 [95%CI 0.45-0.66]) and OS (HR 0.80 [0.70-0.92]). Similar results were seen with abi+apa (0.51 [0.41-0.64], 0.77 [0.65-0.91]). Radiographic progression was associated with significantly higher hazard of death in the state arrival extended Markov proportional hazard model (3.64 [1.54-8.62]) while longer TTrP was associated with reduced hazard of death (0.94 [0.93-0.95]). At the patient level, the correlation between TTrP & OS and rPFS & OS was 0.58 [0.54-0.63] and 0.68 [0.65-0.71], in the overall cohort. In the abi and abi+apa group, the correlation between TTrP and OS was 0.60 [0.53-0.66] and 0.73 [0.66-0.79] and that for rPFS and OS was 0.72 [0.67-0.75] and 0.79 [0.74-0.83], respectively. At the trial level, the treatment effect on rPFS & OS and TTrP & OS were correlated with average R2 of 0.84, 0.84, 0.85, and 0.86, respectively. The mean surrogate threshold effect over 500 permutations for HRrPFS and HRTTrP was 0.78 and 0.70 in ACIS and 0.54 and 0.45 in the COU-AA-302 trials, respectively. Conclusions: TTrP and rPFS were found to have significant association with OS in chemo-naïve mCRPC patients. We noted a modest to strong correlation between the treatment effect on both the ICE and OS at the trial level. Larger meta-analytic studies are needed to validate these findings.

FORMULA-509: A multicenter randomized trial of post-operative salvage radiotherapy (SRT) and 6 months of GnRH agonist with or without abiraterone acetate/prednisone (AAP) and apalutamide (Apa) post-radical prostatectomy (RP)

303

Background: Six months of a GnRH agonist with SRT is a standard of care for patients with unfavorable features and a detectable PSA post-RP. FORMULA-509 was designed to evaluate whether adding six months of AAP and Apa to this regimen could improve outcomes. Methods: FORMULA-509 (NCT03141671) is an investigator-initiated, multi-center, open-label, randomized trial. Patients had PSA≥0.1 post-RP and one or more unfavorable features (Gleason 8-10, PSA>0.5, pT3/T4, pN1 or radiographic N1, PSA doubling time <10 months, negative margins, persistent PSA, gross local/regional disease, or Decipher High Risk). All patients received SRT plus 6 months of GnRH agonist and randomization was to concurrent bicalutamide 50 mg or AAP 1000mg/5mg + Apa 240mg QD. Radiation to pelvic nodes was required for pN1 and optional for pN0. The primary endpoint was PSA progression-free survival (PFS) and secondary endpoint was metastasis-free survival (MFS) determined by conventional imaging. The study was powered to detect a HR of 0.50 for PFS and a HR of 0.30 for MFS, each with 80% power and one-sided type I error of 0.05. Stratification was by PSA at study entry (>0.5 vs.≤0.5) and pN0 vs pN1. Analyses within these subgroups were pre-planned. Results: 345 participants (332 evaluable) from 9 sites were randomized from 11/24/2017 to 3/25/2020 (172 bicalutamide, 173 AAP/Apa). Median follow-up was 34 (6-53) months; 29% were pN1 and 31% had PSA >0.5 ng/mL. The HR for PFS was 0.71 (90% CI 0.49-1.03), stratified one-sided log-rank p=0.06 (3-year PFS was 68.5% bicalutamide vs 74.9% AAP/Apa). The HR for MFS was 0.57 (90% CI 0.33-1.01), stratified one-sided log rank p=0.05 (3-year MFS was 87.2% bicalutamide vs 90.6% AAP/Apa). In a pre-planned analysis by stratification factors, AAP/Apa was significantly superior for patients with PSA >0.5 for PFS [HR 0.50, (90% CI 0.30-0.86), p=0.03 (2-sided); 3-year PFS 46.8% bicalutamide vs. 67.2% AAP/Apa] and for MFS [HR 0.32 (90% CI 0.15-0.72), p=0.01 (2-sided); 3-year MFS 66.1% bicalutamide vs. 84.3% AAP/Apa.] No statistically significant benefit was detected in pre-planned analyses of stratification subgroups defined by PSA≤0.5, pN0, or pN1. Adverse events were consistent with the known safety profiles of the agents being studied, with more rash and hypertension in the AAP/Apa arm. Conclusions: Although this primary analysis did not meet the pre-specified threshold for statistical significance, it does strongly suggest that the addition of AAP/Apa to SRT+6 months of ADT may improve PFS and MFS, particularly in the subgroup of patients with PSA>0.5 where a pre-planned subgroup analysis by stratification factors observed a statistically significant benefit for both PFS and MFS. Clinical trial information: NCT03141671 .

Testosterone Recovery Following Androgen Suppression and Prostate Radiotherapy (TRANSPORT): Individual patient data meta-analysis from the MARCAP Consortium

366

Background: The kinetics of testosterone recovery (TR) vary following cessation of androgen deprivation therapy (ADT) of various durations when given in combination with radiotherapy for prostate cancer. Time to TR will impact on quality of life. We aim to identify factors affecting the time to TR following ADT use. Methods: We included trials of prostate radiotherapy and ADT in the Meta-Analysis of Randomized trials in Cancer of the Prostate (MARCAP) consortium for which prospectively collected serial testosterone data is available. Time to non-hypogonadal TR (NHTR) (>8.0nmol/L) and time to full TR (FTR) (>10.5nmol/L) were estimated from the date of first available testosterone at trial enrolment to the date of TR using the Kaplan-Meier method. The effect of interactions between duration of ADT and patients’ age on TR was evaluated. Results: There were 1439 men with non-castrate testosterone at baseline (>1.7nmol/L) who met the inclusion criteria for analysis, of which 220, 765 and 454 men had 3-, 6-, and 18-months of ADT. There were 959 (67%) men who had FTR at last follow-up. For men who had 3-, 6-, and 18-months of ADT, the median time (range) to NHTR were 5.5 (1.6-76.3), 12.2 (0.8-53.6), and 30.1 (2.8-90.4) months respectively, while the median time (range) to FTR were 6.2 (1.8-75.7), 15.2 (0.8-86.0), and 36.0 (18.1-85.5) months respectively. In the subset of 1160 men who had normal testosterone at baseline (>10.5nmol/L), 851 (69%) men had FTR, with a median time (range) to FTR of 5.5 (1.8-75.7), 12.7 (1.8-86.0), and 30.8 (18.1-84.1) months for men who had 3-, 6- and 18-months ADT, respectively. For any given duration of ADT, men aged above 65 years were less likely to have FTR compared to those aged under 65 years – HR=0.67 (95%CI=0.46-0.99), HR=0.80 (95%CI=0.67-0.96), HR=0.64 (95%CI=0.51-0.81) for men who had 3-, 6-, and 18-months ADT respectively. There was no evidence of interaction between the effect of ADT duration on time to FTR and age (interaction P=0.3 for entire cohort). Conclusions: This is the largest pooled analysis of prospectively collected serial testosterone data from randomized trials, indicating substantial delay in FTR in men receiving longer durations of ADT. Approximately one-third of the men did not achieve FTR, which may have life-long impact on quality of life.

Use of prostate cancer subtyping by gene expression to predict response to radiation and chemohormonal therapies

241

Background: We previously reported on the use of gene expression profiling to characterize four primary subtypes in an analysis of over 100,000 prostate cancer primary tumors. Here we examine these subtypes and response to radiation (RT) after prostatectomy or chemotherapy in addition to androgen deprivation therapy (ADT) in hormone-sensitive metastatic prostate cancer (mHSPC). Methods: We examined a 215-gene prostate subtyping classifier (PSC) which groups luminal and basal gene expression profiles into one of four subtypes; luminal differentiated (LD), luminal proliferating (LP), basal immune (BI) and basal neuroendocrine-like (BN). The log-rank method was used to compare (i) metastasis-free survival between patients who did and did not receive salvage RT in the META855 cohort of localized disease patients treated with radical prostatectomy (n=855) and the (ii) overall survival of patients on the Phase III mHSPC EA3805 CHAARTED trial of ADT or ADT + docetaxel chemotherapy (n=160). Results: After radical prostatectomy, patients with BI tumors derived benefit from RT in terms of metastasis-free survival ( P=9.23e-4) while those with other subtype tumors did not (Each Log-rank P≥0.5). Patients with metastatic disease and LP tumors derived benefit from docetaxel (Log-rank P=0.002) while those with other subtypes tumors did not (Log-rank P=0.2). Conclusions: Basal-luminal subtyping segments tumors by relevant biological processes with potential implications for identifying patients who benefit from salvage radiation post prostatectomy and addition of docetaxel to ADT in mHSPC.

Determining the impact of genomic classifier testing on patient-reported quality of life after prostatectomy: Results from the G-MINOR randomized trial

345

Background: Decipher is a tissue-based genomic classifier (GC) developed and validated in the post-radical prostatectomy (RP) setting to help guide adjuvant treatment decisions for prostate cancer (PCa). We conducted the first prospective, randomized trial assessing the impact of GC testing on adjuvant therapy use. Here, we determine the impact of GC testing on patient reported (PRO) quality of life outcomes (QoL) in men at high-risk of post-RP recurrence. Methods: The G-MINOR trial is a prospective, unblinded, randomized trial which enrolled 356 patients from 12 centers in the Michigan Urological Surgery Improvement Collaborative (MUSIC). Patients were enrolled between Aug 2016-July 2018. Eligible patients had undergone RP within 9 months of enrollment, had pT3-4 disease and/or positive surgical margins, and a post-RP PSA <0.1ng/mL. Patients were assigned to either the GC or usual-care (UC) group using cluster-crossover block randomization assignments. Evaluable patients (338) were followed for at least 18 months. PROs were obtained using the Expanded Prostate Cancer Index Composite (EPIC-26) survey at baseline (before RP), 3, 6, 12, and 24 months after RP. Results: A total of 226/338 evaluable men (67%) had PRO data for this analysis (116 UC arm/110 GC arm). Median age was 65 years. Of the 226 men included in the PRO analysis, a total of 23 (9 UC arm/14 GC arm) had adjuvant treatment (p = 0.22). At 12 months follow-up, those in the GC arm had no significant change in adjusted mean difference in domain score from baseline compared to those in the UC arm for urinary irritative (UIR) function (1.0, 95% CI [-2.9– 4.9], p=0.6), urinary incontinence (UI) (0.8, 95% CI [-5.1– 6.7], p=0.8), or sexual function (SF) (0.5, 95% CI [-6.9– 7.9], p=0.9). This remained true at 24 months for all three domains [UIR; (2.3, 95% CI [-2.1– 6.6], p=0.3)], [UI; (-0.3, 95% CI [-7.3– 6.7], p=0.9)], [SF; (1.5, 95% CI [-6.8– 9.7], p=0.7)]. Conclusions: In the first ever randomized trial testing the clinical utility of a GC test in localized PCa, longitudinal patient reported QOL outcomes were not significantly different between men who underwent risk stratification with or without Decipher. Clinical trial information: NCT02783950 .

Clinical impact of mutations in driver oncogenes and TP53/RB1 in advanced prostate cancer

263

Background: Prostate cancer (PCa) is characterized by considerable genetic heterogeneity, and complex genomic features may influence prognosis and treatment response. We created a database of aggressive PCa that integrates comprehensive genomic sequencing with detailed clinical outcomes to better understand the optimal use of genomic sequencing. Methods: From 4/2005-7/2021, PCa cancer patients older than 18 years of age underwent tissue collection for tumoral RNA-sequencing and tumor/normal whole exome sequencing at our institution (HUM00046018, HUM00048105, HUM00067928, SU2C). Genomic and transcriptomic sequencing data was processed using Turnkey Precision Oncology. Genetic alterations, including ETS fusions, SPOP, FOXA1 class 1, and CDK12 mutations, as well as TP53 and RB1 mutations were analyzed. Clinical data was collected from 05/2021-01/2022, and clinical associations (metastasis free survival (MFS), time to castrate resistant prostate cancer (CRPC), and overall survival (OS)) were determined. Results: Data was available for 325 men. Median follow up from diagnosis was 106 months (IQR, 90-121), median age at diagnosis was 61 (IQR, 54-67), and most (91%) presented with PCa adenocarcinoma (n=292/325). At diagnosis, 51% (n=165) had localized, 5% (n=18) had clinical node positive, and 40% (n=128) had de-novo M1 disease. At time of tissue sampling, 87% (n=283) had metastatic disease, and 59% (n=192) were castrate resistant. Established PCa driver mutations included 140 ETS fusions (49%), 26 SPOP mutations (9%), 22 FOXA1 class 1 mutations (8%), and 15 (5%) CDK12 mutations. For men with localized disease at diagnosis (n=197/325), ETS fusion was associated with improved MFS (HR: 0.55; 95% CI: 0.37-0.81), time to CRPC (HR: 0.53; 0.35-0.80), and OS (HR: 0.56; 0.35-0.89). SPOP mutations were also associated with improved prognosis in this population (n=197/325): MFS (HR: 0.45; 0.24-0.84), time to CRPC (HR: 0.36; 0.18-0.73), and OS (HR: 0.46; 0.21-0.99). TP53 mutations were identified in 38% (n=122) of all patients and were associated with worse OS from the time of biopsy after adjusting for PCa castration state and disease spread at biopsy (HR: 2.2; 1.7-2.9, p<0.001). RB1 mutations were identified in 12% (n=40; 24/40 also TP53 mutants). OS from the time of biopsy was worse in the presence of dual TP53/RB1 mutants when compared to TP53 or RB1 mutants alone, independent of the disease state at time of biopsy (HR, 4.3; 95%CI: 2.7-7.0). Conclusions: In a cohort of aggressive PCa, oncogenic driver mutations were associated with significant differences in prognosis. ETS fusions and SPOP mutations correlated with improved outcomes for men with localized disease at presentation. TP53 loss was associated with worse prognosis, as was the combination with RB1 loss, across the disease spectrum. Future efforts will focus on correlating sensitivity to PCa treatments with genetic alterations throughout the disease course.

Patient-level data meta-analysis of a multi-modal artificial intelligence (MMAI) prognostic biomarker in high-risk prostate cancer: Results from six NRG/RTOG phase III randomized trials

299

Background: Recently, an MMAI prognostic biomarker, ArteraAI Prostate, was trained and validated in localized prostate cancer to more accurately risk stratify patients for multiple endpoints compared to NCCN risk groups (Esteva et al., 2022). Prognostication within an NCCN risk group remains clinically important given the multiple treatment decisions required within each risk group (e.g., radiotherapy dose or hormone therapy use). Herein, we validated the MMAI biomarker in high-risk prostate cancer where an increasing number of therapeutic decisions is required. Methods: This study leveraged histopathology image and clinical data from patients with at least one high-risk feature (HRF; cT3-cT4, Gleason 8-10, PSA > 20 ng/mL, primary Gleason pattern 5) from six NRG/RTOG phase III randomized trials (n=1,088). Patients from two trials not part of the initial MMAI biomarker training/validation (RTOG 0521 [n=344] and 9902 [n=318]) and the MMAI validation cohort (RTOG 9202, 9408, 9413, and 9910 [n=426]) were included. Fine-Gray, cumulative incidence, and time dependent area under the curve (tdAUC) analyses were performed for time to distant metastasis (DM) and prostate cancer-specific mortality (PCSM) for standard clinicopathologic variables (age, PSA, Gleason score, T-stage, number of HRFs) and the MMAI model, as a continuous score (per standard deviation increase) and categorically by quartile. Death from other causes were treated as competing risks. Results: The analyzed cohort had a median follow-up of 10.4 years. Median PSA was 21 ng/mL, 60% had Gleason 8-10 disease, 37% had cT3-T4 disease, and 20% were African American. On univariable analysis, the MMAI model was significantly associated with DM (subdistribution hazard ratio [sHR] 2.05, 95% CI 1.74-2.43, p<0.001) and PCSM (sHR 2.04, 95% CI 1.73-2.42, <0.001). On multivariable analysis, the MMAI model, adjusting for either age, PSA, Gleason score, T-stage, or number of HRFs, was the only variable significantly associated with DM. TdAUC was highest for the MMAI biomarker for both 5-year DM (0.71), compared to PSA (0.56), Gleason score (0.61), T-stage (0.63), or number of HRFs (0.64), and for 5-year PCSM (0.75), compared to clinicopathologic variables (range 0.53-0.63). The estimated 10-year DM and 15-year PCSM rates for MMAI quartile 1 vs 4 were 8% vs 31% and 8% vs 34%, respectively. Conclusions: Our novel MMAI prognostic biomarker was successfully validated across six phase III randomized trials with long-term follow-up to be independently prognostic over standard clinical and pathologic variables for men with high-risk prostate cancer. Despite all patients having high-risk disease, the MMAI biomarker identified those with highly variable risks for DM and PCSM. This tool can help enable personalized, shared decision making for patients and providers.

Biochemical recurrence (BCR) surrogacy for clinical outcomes after radiotherapy for adenocarcinoma of the prostate (BCRSCRAP): A meta-analysis from MARCAP Consortium

391

Background: Event-free survival, a PSA-driven endpoint, was shown to not be surrogate endpoint for overall survival (OS) in the ICECAP two-stage meta-analytic approach. However, time to biochemical recurrence (TTBCR) in NRG/RTOG 9202 met Prentice criteria for surrogacy. We performed an individual patient data (IPD) meta-analysis of 11 randomized controlled trials evaluating RT dose escalation, ADT use, and adjuvant ADT prolongation to evaluate the surrogacy of time to BCR (TTBCR), censoring for non-prostate cancer deaths, using both approaches to evaluate surrogacy. Methods: This individual patient level meta-analysis was performed using data from the MARCAP consortium, and 11 radiotherapy trials were included. TTBCR was defined as time to developing a BCR or experiencing prostate cancer-specific mortality (PCSM), with censoring at time of other-cause death or loss to follow-up. Landmark analyses were used to test the Prentice criteria for surrogacy. For patient level correlation between TTBCR and OS, we applied a bivariate Copula model to estimate the Kendall’s τ. For trial level correlation of the treatment effect on TTBCR and true endpoints, a weighted linear regression model was applied between the effects of treatment (natural log of hazard ratio [log-HR]) on OS versus TTBCR using a weightage that was inverse variance of BCR log-HR estimate. Results: Based on Prentice criteria, BCR at the landmark time point of 48 months was associated with increased risk of mortality in trials that compared treatment intensification with adjuvant ADT prolongation (HR 2.18 [95% CI 1.95-2.42]), the addition of ADT (HR 1.38 [1.25-1.54]), and RT dose escalation (HR 2.12 [1.83-2.46]) on uni- and multi-variable analyses. At the patient level, there was a low to moderate level correlation between BCR and OS with Kendall’s τ of 0.34 and a R2 of 0.55 for correlation of treatment effect on TTBCR and OS. At the trial level, there was a poor correlation between treatment effect on TTBCR and OS (R2=0.16). Conclusions: This IPD meta-analysis demonstrates that while BCR is prognostic, it is not a surrogate endpoint for OS in localized prostate cancer for patients treated with a diverse array of radiotherapeutic strategies. This highlights the importance of other cause mortality in prostate cancer. Our results highlight the differences in interpretability of Prentice criteria and the two-stage meta-analytic approach and suitability of endpoints for clinical trial design.

A multi-center, prospective, observational study of patients with prostate cancer being treated with relugolix: OPTYX

TPS398

Background: Androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) receptor agonists or antagonists are the foundation of advanced prostate cancer (aPC) treatment. Relugolix is an oral non-peptide GnRH receptor antagonist approved in the US for the treatment of aPC. In the phase 3 HERO trial, relugolix maintained suppression of testosterone to castration levels in 96.7% of men from Day 29 to 48 weeks, with superiority to leuprolide acetate. Relugolix was well tolerated and associated with a 54% lower risk of major adverse cardiovascular events relative to leuprolide acetate (Shore N, NEJM 2020;382;23). The goal of this current study (OPTYX) is to generate real-world evidence about the safety and effectiveness of relugolix in patients with prostate cancer during routine clinical care. Methods: This prospective observational cohort study (registry) is enrolling patients who have planned initiation with relugolix within 1 month prior to the time of study enrollment. The study is designed to prospectively understand the actual experience of patients with prostate cancer treated with relugolix through data collection on patients selected for treatment, treatment patterns, adherence, patient reported quality of life (QoL) and safety data. Additionally, a better understanding of the trajectory of patients with prostate cancer following cessation of relugolix therapy will be gained by observing the clinical course of the disease, health outcomes, and health-related quality-of-life (HRQoL) in these patients. Inclusion criteria include patients > 18 years old with prostate cancer and planned total treatment with relugolix of at least 4 months. Estimated enrollment is 1000 patients, and patients will be followed for up to 5 years. In addition to assessing routine clinical care and disease progression, patient reported outcomes will be assessed with the Functional Assessment of Cancer Therapy-Prostate (FACT-P) for HRQoL and Simplified Medication Adherence Questionnaire (SMAQ) for adherence at 3 and 6 months then every 6 months. Clinical trial information: NCT05467176 .

Prostate cancer risk in African American men evaluated via digital histopathology multi-modal deep learning models developed on NRG Oncology phase III clinical trials

108

Background: Artificial intelligence (AI) tools can display racial bias as a result of existing systemic health inequities and biased datasets. We have previously developed multi-modal AI (MMAI) prognostic models based on digital pathology images from five phase III randomized radiotherapy prostate cancer trials that outperform NCCN risk groups for prediction of distant metastasis (DM), biochemical failure (BF), prostate cancer-specific mortality (PCSM) and all-cause mortality (OS). In this study, we assessed the algorithmic fairness of the locked MMAI models between African American (AA) and non-AA populations in the five randomized trials. Methods: Patients enrolled in NRG/RTOG 9202, 9408, 9413, 9910, and 0126 with digitized biopsy histopathology slides were included in this study. The locked MMAI models were applied, and subgroup analyses were conducted by comparing distributions of clinical variables and MMAI scores (medians for continuous variables and proportions for categorical variables reported), and evaluating MMAI models’ prognostic ability among AA and non-AA men. The performance of the models were compared using DM as the primary endpoint and secondary endpoints of BF, PCSM, OS (death without an event as a competing risk) with Fine-Gray or Cox Proportional Hazards models. Either Kaplan Meier or cumulative incidence estimates were computed and compared using log-rank or Gray’s test. Results: This study included 5,624 men: 932 (17%) AA, 4503 (80%) white, and 189 (3%) other races. AA had younger median age (69 vs 71 year [yr]), higher median baseline PSA (12 vs 10 ng/mL), more T1-T2a (62% vs 57%), more Gleason < 7 (42% vs 36%) and 8-10 (15% vs 12%), and more NCCN low and high risk (12% vs 10% and 41% vs 33%). AA and non-AA had estimated 5-yr BF rates 27% and 27%, 5-yr DM rates 5% and 5%, 10-yr PCSM 5% and 7%, and 10-yr OS 58% and 60%, respectively. The median (interquartile range) score of the model optimizing for 5-yr DM (5-yr DM MMAI) was 0.044 (0.037–0.059) in AA and 0.043 (0.036–0.057) in non-AA. Similarly, all other MMAI models had differences in the medians between AA and non-AA ranging from 0.001 to 0.02. For all endpoints, the 5-yr DM MMAI model showed strong prognostic signal (hazard ratio [HR] per one standard deviation increase: 1.6 for DM, 1.4 for BF, 1.6 for PCSM and 1.3 for OS, all p-values < 0.001) and had comparable trends within AA vs. non-AA in the entire cohort (e.g., HR for DM 1.4 vs 1.6). Similar results were observed for the MMAI model optimizing for 10-yr PCSM. Conclusions: To our knowledge, this represents the first comparative analyses of a digital pathology AI prognostic model in AA vs. non-AA prostate cancer patients. The prognostic performance of the AI models was found to be comparable between subgroups. Our data supports the use of these models across racial groups, though further validation in AA cohorts is ongoing.

Treatment patterns and outcomes in prostate cancer patients tested with Decipher in SEER

e17006

Background: In 2021, national data between the Decipher 22-gene prognostic gene expression classifier (GC) for men with prostate cancer and the Surveillance, Epidemiology, and End Results (SEER) cancer registries were linked. The purpose of the work is to report on the linkage by characterizing national GC usage and its association with treatment decisions for men with prostate cancer. Methods: Patients in the SEER registries with primary prostate cancer diagnosis from 2010 to 2018 were included and linked to data from GC testing conducted between 2014 to 2020 (Veracyte, San Diego, CA). GC scores (range 0-1) and GC risk groups (low, intermediate, and high) were used for continuous and categorical analyses. Multivariable logistic regression was used to quantify the association between GC and active surveillance and watchful waiting (AS/WW) use and adverse pathology at radical prostatectomy (RP). Adverse pathology was defined as pathological grade group ≥3, pathological stage ≥pT3b, or lymph node invasion. Results: A total of 575,363 patients were eligible for analysis, of which 10,528 patients underwent GC testing (5,015 GC biopsy test, and 5,513 GC RP test). The median age was 67 for both tested and untested, but more white patients underwent testing (82% vs 76%, p < 0.001). For GC biopsy tested patients, AS/WW was highest for those with GC low risk results (41%) as compared to those with intermediate (32%) or high (17%) GC risk (p < 0.001). RP rates were lower in the tested compared to untested (25% vs. 36%, p < 0.001), and among the tested patients, RP use increased by GC risk group (19% of low, 25% of intermediate, and 34% of high GC risk, p < 0.001). A similar trend by GC risk group in management for radiation therapy was observed (13% of low, 19% of intermediate, and 29% of high GC risk, p < 0.001). In a multivariable logistic regression adjusted for age, race, NCCN risk group, and year of diagnosis, GC tested patients were more likely to undergo AS/WW compared to untested (OR 2.9 [95% CI, 2.8-3.1], p < 0.001). Within the subset of patients classified as NCCN low/favorable intermediate risk at biopsy and who were subsequently treated with RP (n = 594), GC high risk (> 0.6) was associated with more than 3 times the odds of harboring adverse pathology (OR 3.2 [95% CI 1.6-6.4], p < 0.001). Conclusions: Using the first ever linked SEER-Decipher data, we demonstrate that population-based treatment patterns are independently associated with GC test results. Patients with lower GC scores are independently more likely to undergo AS/WW; those with higher scores are more likely to have adverse pathology at time of RP.

Candidate surrogate endpoints in advanced prostate cancer: Aggregate meta-analysis of 143 randomized trials

5039

Background: The Intermediate Clinical Endpoints (ICEs) in Cancer of the Prostate (ICECaP) working group identified metastasis-free survival as a valid surrogate endpoint for overall survival (OS) for patients with localized prostate cancer. No comparably validated surrogate endpoints for OS exist in advanced prostate cancer. Methods: In this meta-analysis, PubMed was searched for trials in advanced prostate cancer, defined as node positive (N1M0), metastatic castration-sensitive (mCSPC), non-metastatic (M0CRPC), or metastatic castration-resistant prostate cancer (mCRPC). Eligible randomized trials were required to report OS and ≥1 intermediate clinical endpoint (ICE). ICEs included biochemical-failure (BF), clinical failure (CF), BF-free survival (BFS), progression-free survival (PFS), radiographic PFS (radiographic +/- other study defined endpoints). Candidacy for surrogacy was assessed using the second condition of the meta-analytic approach, correlation of the treatment effect of the ICE and OS, using R2 weighted by the inverse variance of the log ICE hazard ratio and defined as an R2 > 0.70. Results: A total of 143 randomized trials (n = 75,601 patients) were included. No candidate endpoints met criteria for surrogacy; R2 BF (n = 28,922) 0.42 (95%CI 0.18-0.64), BFS (n = 25,741) 0.57 (95%CI 0.37-0.73), CF (n = 22,616) 0.31 (95%CI 0.0075-0.56), PFS (n = 52,639) 0.50 (95%CI 0.35-0.63), and radiographic PFS (n = 52,548) 0.50 (95%CI 0.35-0.63). Within preplanned subgroups by castration sensitive or resistant disease, or by treatment type, neither BFS nor PFS met criteria for surrogacy. When assessing radiographically-defined progression (exclusive or with clinical progression), PFS for the overall group and by castration status did not meet criteria for surrogacy. Sensitivity analyses demonstrated that candidacy for surrogacy of all endpoints tested did not change over time. Conclusions: Our aggregate screening method for surrogate endpoints in advanced prostate cancer demonstrated commonly used clinical endpoints are not valid surrogate endpoints for OS, and further composite endpoint construction is necessary.

Validation of the performance of the Decipher biopsy genomic classifier in intermediate-risk prostate cancer on the phase III randomized trial NRG Oncology/RTOG 0126

269

Background: The 22-gene Decipher genomic classifier (GC) is a prognostic biomarker that has been validated in phase III trials in high-risk localized, post-prostatectomy, and metastatic and non-metastatic castration-resistant prostate cancer. Herein, we report the first validation of the biopsy GC in intermediate-risk prostate cancer from the phase III randomized trial NRG/RTOG 0126. Methods: After National Cancer Institute approval, biopsy slides were collected from the NRG biobank from RTOG 0126, a phase III randomized trial of men with intermediate-risk prostate cancer randomized to 70.2 Gy versus 79.2 Gy of radiotherapy without the use of concomitant hormone therapy. RNA was extracted from the highest grade tumor foci and processed through a quality control (QC) pipeline prior to generation of the previously locked 22-gene GC model. After GC data was generated it was linked with clinical outcomes to assess prognostic performance. The primary endpoint for this ancillary project was disease progression, defined as biochemical failure, local failure, distant metastasis or prostate cancer-specific mortality, as well as use of salvage therapy. Secondary endpoints included the previous individual endpoints, metastasis-free survival, and overall survival. Independent GC prognostic performance was assessed using cause-specific Cox or competing risk adjusted Fine-Gray multivariable models that included randomization arm and prognostic stratification factors. Death without events were treated as competing risks. Results: A total of 215 patient samples passed QC of the 449 that had suitable cDNA for expression analysis. The median follow-up was 12.8 years (range 2.4-17.7), and 61% had Gleason 3+4, 24% had Gleason 4+3, and the median PSA was 7.2 ng/mL (IQR 5.0-10.2). On multivariable analysis the 22-gene GC (per 0.1 unit) was independently prognostic for disease progression (subdistribution hazard ratio [sHR] 1.13, 95%CI (1.01-1.26), p = 0.03), biochemical failure (sHR 1.23, 95%CI 1.10-1.37, p < 0.001), distant metastasis (sHR 1.28, 95%CI 1.06-1.54, p = 0.01), and PCSM (sHR 1.45, 95%CI 1.20-1.76, p < 0.001). In patients with lower GC scores the 10-year distant metastasis rate difference between the 70.2 Gy and 79.2 Gy was 5%, as compared with 26% for higher GC patients. Conclusions: This study represents the first validation of any biopsy-based gene expression classifier in intermediate-risk prostate cancer. Decipher is independently prognostic and can identify patients that have low rates of metastatic events despite not receiving concurrent hormone therapy, and can be used to help personalize therapy in this setting. Clinical trial information: NCT00033631.

Development and validation of a prognostic AI biomarker using multi-modal deep learning with digital histopathology in localized prostate cancer on NRG Oncology phase III clinical trials

222

Background: Prognostication in localized prostate cancer is reliant on non-specific tools, an issue that leads to the over- and under-treatment of patients. Various tissue-based molecular biomarkers have attempted to fill this unmet need, but most lack prospective randomized trial validation. Herein, we train and validate prognostic biomarkers in localized prostate cancer using five phase III randomized trials, by leveraging multi-modal deep learning on digital histopathology. Methods: Histopathology image data was generated from pre-treatment biopsy slides in five NRG Oncology phase III randomized radiotherapy prostate cancer trials (RTOG 9202, 9408, 9413, 9910, and 0126). The trials were randomly split into training (80%) and validation (20%) cohorts. A multi-modal artificial intelligence (MMAI) architecture was developed to take clinicopathologic and image-based (histopathology) data as input and predict binary outcomes. Using this architecture, various models were trained to predict relevant clinical endpoints: biochemical recurrence (BCR), distant metastasis (DM), prostate cancer-specific survival (PCaSS), and overall survival (OS). These models were then validated for measures of prognostic discrimination using the time-based area under the curve (AUC) method. Results: Clinicopathologic and histopathology image data was available for 5,654 of 7,957 eligible patients (71.1%), yielding 16.1 TB of data from 16,204 histopathology slides of pretreatment biopsy samples. After training the models, locking them, and evaluating them on the validation cohort, we found that the MMAI prognostic model had superior discrimination compared to the NCCN model (PSA, T-stage, and Gleason score) for 5-year DM (AUC of 0.84 vs 0.73), 5-year BCR (AUC of 0.69 vs 0.58), 10-year PCaSS (AUC of 0.79 vs 0.66), and 10-year OS (AUC of 0.65 vs 0.58). Within each of the individual trials in the validation cohort, the MMAI-model had superior performance compared to NCCN risk groups for all clinical endpoints. Conclusions: This represents the first ever development and validation of prognostic biomarkers in localized prostate cancer using multiple large phase III clinical trials. We have successfully validated that our MMAI-prognostic biomarkers are superior to standard clinical and pathologic variables in identifying future BCR, DM, PCaSS, and OS. This massively scalable technology is feasible and can help personalize the management of prostate cancer patients. Funding: This project was supported by grants U10CA180868 (NRG Oncology Operations), U10CA180822 (NRG Oncology SDMC), UG1CA189867 (NCORP), U24CA196067 (NRG Specimen Bank) from the National Cancer Institute (NCI).

An AI-derived digital pathology-based biomarker to predict the benefit of androgen deprivation therapy in localized prostate cancer with validation in NRG/RTOG 9408

223

Background: The current standard of care for men with intermediate- and high-risk localized prostate cancer treated with radiotherapy (RT) is the addition of androgen deprivation therapy (ADT). Presently, there are no validated predictive biomarkers to guide ADT use or duration in such men. Herein, we train and validate the first predictive biomarker for ADT use in prostate cancer using multiple phase III NRG Oncology randomized trials. Methods: Pre-treatment biopsy slides were digitized from five phase III NRG Oncology randomized trials of men receiving RT with or without ADT. The training set to develop the artificial intelligence (AI)-derived predictive biomarker included NRG/RTOG 9202, 9413, 9910, and 0126, and was trained to predict distant metastasis (DM). A multimodal deep learning architecture was developed to learn from both clinicopathologic and digital imaging histopathology data and identify differential outcomes by treatment type. After the model was locked, an independent biostatistician performed validation on NRG/RTOG 9408, a phase III randomized trial of RT +/- 4 months of ADT. The DM rates were calculated using cumulative incidence functions in biomarker positive and negative groups, and biomarker-treatment interaction was assessed using Fine-Gray regression such that death without DM was treated as a competing event. Results: Clinical and histopathological data was available for 5,654 of 7,957 eligible patients (71.1%). The training cohort included 3,935 patients and had a median follow-up of 13.6 years (IQR [10.2, 17.7]). After the AI-derived predictive ADT classifier was trained, it was validated in NRG/RTOG 9408 (n = 1719, median follow-up 17.6 years, IQR [15.0, 19.7]). In the NRG/RTOG 9408 validation cohort that had digital histopathology data, ADT significantly improved DM (HR 0.62, 95% CI [0.44, 0.87], p = 0.006), consistent with the published trial results. The biomarker-treatment interaction was significant (p-value = 0.0021). In patients with AI-biomarker positive disease (n = 673, 39%), ADT had a greater benefit compared to RT alone (HR 0.33, 95% CI [0.19, 0.57], p < 0.001). In the biomarker negative subgroup (n = 1046, 61%), the addition of ADT did not improve outcomes over RT alone (HR 1.00, 95% CI [0.64, 1.57], p = 0.99). The 15-year DM rate difference between RT versus RT+ADT in the biomarker negative group was 0.3%, vs biomarker positive group 9.4%. Conclusions: We have successfully validated in a phase III randomized trial the first predictive biomarker of ADT benefit with RT in localized intermediate risk prostate cancer using a novel AI-derived digital pathology-based platform. This AI-derived predictive biomarker demonstrates that a majority of patients treated with RT on NRG/RTOG 9408 did not require ADT and could have avoided the associated costs and side effects of this treatment.

Local failure, distant metastasis, and survival after definitive radiotherapy for intermediate- and high-risk prostate cancer: An individual patient-level meta-analysis of 18 randomized trials

277

Background: The prognostic importance of local failure (LF) after definitive radiotherapy (RT) in patients with NCCN intermediate- (IRPCa) and high-risk prostate cancer (HRPCa) remains unclear, particularly given the likelihood that occult distant metastases (DMs) at presentation may be the true driver of natural history. Here, we leverage individual patient data (IPD) from 18 randomized control trials (RCTs) to evaluate the prognostic impact of LF and the kinetics of DM after RT. Methods: IPD for 18 RCTs were obtained from the Meta-Analysis of Randomized trials in Cancer of the Prostate (MARCAP) Consortium, comprising a total of 12533 patients (6288 HRPCa & 6245 IRPCa). Multivariable Cox proportional hazards (PH) models were developed to evaluate the relationship between overall survival (OS), PCa-specific survival (PCSS), DM-free survival (DMFS) & LF as a time-dependent covariate, adjusted for clinicodemographic parameters. Markov PH models, defined via transitions between 4 states, were developed to evaluate the aforementioned relationship. Proportional hazards assumption was imposed and examined for both models. Time is from randomization. Results: Median follow-up was 9.1 years. There were 795 (13%) LF & 1288 (21%) DM events for patients with HRPCa; these numbers were 449 (7%) & 451 (7%) for IRPCa. For HRPCa & IRPCa, 81% and 81% of DMs developed from a clinically relapse-free state (cRFS), with a median time of 46 and 60 months, respectively (p < 0.0001). 39% & 13% of DM events occurred within 2 years after RT for HRPCa & IRPCa, respectively. At later time points, DM events were more likely to emerge after an LF event for both HRPCa (9% vs. 34% between 0-2 vs. 8-10 years post-RT, p = 0.001) and IRPCa (10% vs. 34% between 0-2 vs. 8-10 years post-RT, p = 0.008). LF was significantly associated with OS (hazard ratio [HR] 1.17, 95% confidence interval [CI] 1.06–1.30), PCSS (HR 2.02, 95% CI 1.75-2.33) & DMFS (HR 1.94, 95% CI 1.75–2.15) (p < 0.01 for all) in patients with HRPCa. LF was also significantly associated with DMFS (HR 1.57, 95% CI 1.36–1.81) but not OS in patients with IRPCa. Patients who had not transitioned to the LF state had a significantly lower HR of transitioning to a PCa-specific death state than those who transitioned to the LF state (HR 0.32, 95% CI 0.21–0.50, p < 0.001). Conclusions: LF is an independent prognosticator of OS, PCSS & DMFS in HRPCa and of DMFS in IRPCa. The predominant mode of DM development is from the cRFS state, underscoring the importance of accurate upfront staging & systemic therapy. However, particularly at late time points, an increasing proportion of DM events originated after diagnosis of a LF, constituting a “second wave” of DM events. This suggests that optimizing local control is also important, though the majority of DM events appear prior to a clinically-detected LF.

Transcriptional profiling of primary prostate tumor in metastatic hormone-sensitive prostate cancer and association with clinical outcomes: correlative analysis of the E3805 CHAARTED trial

BACKGROUND

The phase III CHAARTED trial established upfront androgen-deprivation therapy (ADT) plus docetaxel (D) as a standard for metastatic hormone-sensitive prostate cancer (mHSPC) based on meaningful improvement in overall survival (OS). Biological prognostic markers of outcomes and predictors of chemotherapy benefit are undefined.

PATIENTS AND METHODS

Whole transcriptomic profiling was performed on primary PC tissue obtained from patients enrolled in CHAARTED prior to systemic therapy. We adopted an a priori analytical plan to test defined RNA signatures and their associations with HSPC clinical phenotypes and outcomes. Multivariable analyses (MVAs) were adjusted for age, Eastern Cooperative Oncology Group status, de novo metastasis presentation, volume of disease, and treatment arm. The primary endpoint was OS; the secondary endpoint was time to castration-resistant PC.

RESULTS

The analytic cohort of 160 patients demonstrated marked differences in transcriptional profile compared with localized PC, with a predominance of luminal B (50%) and basal (48%) subtypes, lower androgen receptor activity (AR-A), and high Decipher risk disease. Luminal B subtype was associated with poorer prognosis on ADT alone but benefited significantly from ADT + D [OS: hazard ratio (HR) 0.45; P = 0.007], in contrast to basal subtype which showed no OS benefit (HR 0.85; P = 0.58), even in those with high-volume disease. Higher Decipher risk and lower AR-A were significantly associated with poorer OS in MVA. In addition, higher Decipher risk showed greater improvements in OS with ADT + D (HR 0.41; P = 0.015).

CONCLUSION

This study demonstrates the utility of transcriptomic subtyping to guide prognostication in mHSPC and potential selection of patients for chemohormonal therapy, and provides proof of concept for the possibility of biomarker-guided selection of established combination therapies in mHSPC.

Patient-Reported Outcomes From a Phase 3 Randomized Controlled Trial Exploring Optimal Sequencing of Short-Term Androgen Deprivation Therapy With Prostate Radiation Therapy in Localized Prostate Cancer

PURPOSE

Two phase 3 randomized controlled trials (OTT-0101, RTOG-9413) and a meta-analysis have shown an impact of sequencing of androgen deprivation therapy (ADT) and radiation therapy on oncologic outcomes in prostate cancer (PCa). However, the impact of sequencing strategy on health-related quality of life (HR-QoL) is unclear. Here, we present the patient-reported HR-QoL outcomes from the OTT-0101 study.

METHODS AND MATERIALS

In this trial, patients with PCa with Gleason score ≤7, clinical stage T1b to T3a, and prostate-specific antigen level <30 ng/mL were randomly assigned to neoadjuvant and concurrent ADT for 6 months, starting 4 months before or concurrent with prostate radiation therapy, or concurrent and adjuvant ADT for 6 months, starting simultaneously with prostate radiation therapy. HR-QoL was assessed using European Organisation for Research and Treatment of Cancer QoL questionnaires. Time until definitive deterioration was defined as time from random allocation to the first deterioration of at least 10 points with no further improvement of ≥10 points or if the patient experienced progression, died, or dropped out after deterioration, resulting in missing data. Stratified log-rank tests were applied for between-group comparisons of time-to-event estimates.

RESULTS

Overall, 393 patients (194 and 199 in the 2 arms, respectively) were evaluable, except 214 (101 and 113 in the 2 arms, respectively) for sexual function. Five-year rates of freedom from definitive deterioration of urinary symptoms, bowel symptoms, and sexual activity were 33.5%, 33.1%, and 38.5% in the neoadjuvant group and 34.1%, 35.4%, and 36.7% in the adjuvant group, respectively, with no significant between-group differences. The adjuvant approach was associated with a reduced risk of definitive deterioration of sexual function (hazard ratio, 0.68; 95% confidence interval, 0.49-0.94; P = .02). With respect to clinical relevance, the mean change in score for sexual function showed only a small to moderate difference favoring the adjuvant group at and beyond 3 years.

CONCLUSIONS

In this study, no differences were found in the bowel or urinary symptoms between the adjuvant and neoadjuvant approach. Considering a significant likelihood of type I and type II errors and because of a lack of a persistent and clinically meaningful between-group difference in mean score changes over time, our findings do not confer a clear and conclusive picture of the impact of sequencing strategy on sexual function.

Validation of the decipher genomic classifier (GC) in SAKK 09/10: A phase III randomized trial of dose-escalated salvage radiotherapy (SRT) after radical prostatectomy (RP)

5010

Background: GC has been shown to independently prognosticate outcomes in prostate cancer. Herein, we validate the GC in a European randomized phase III trial of dose escalated SRT after RP. Methods: SAKK 09/10 (NCT01272050) randomized 350 patients with biochemical recurrence after RP to 64Gy vs 70Gy. No patients received androgen deprivation therapy (ADT) or pelvic nodal radiotherapy. A pre-specified statistical plan was developed to assess the impact of the GC on clinical outcomes. RP samples were centrally reviewed for the highest-grade tumor and those passing quality control (QC) were run on a clinical-grade whole-transcriptome assay to obtain the GC score (0 to 1; < 0.45, 0.45-0.6, > 0.6 for low-, intermediate-, and high, respectively). The primary aim of this study was to validate the GC for the prediction of freedom from biochemical progression (FFBP) using Cox multivariable analysis (MVA) adjusting for age, T-category, Gleason score, persistent PSA after RP, PSA at randomization, and randomization arm. The secondary aims were to evaluate the association of GC with clinical progression-free survival (CPFS) and use of salvage ADT. Results: Of 233 patients with tissue available, 226 passed QC and were included for analysis. The final GC cohort was a representative sample of the overall cohort, with a median follow-up of 6.3 years (IQR 6.0-7.2). GC score (continuous per 0.1 unit, score 0-1) was independently associated with FFBP (HR 1.14 [95% CI 1.03-1.25], p = 0.009). Higher GC scores were independently associated with CPFS, use of salvage ADT, and rapid biochemical failure ( < 18 months after SRT). High- vs. low/intermediate-GC showed a HR of 2.22 ([95% CI 1.37-3.58], p = 0.001) for FFBP, 2.29 ([95% CI 1.32-3.98], p = 0.003) for CPFS, and 2.99 ([95% CI 1.50-5.95], p = 0.002) for use of salvage ADT. Patients with high-GC had 5-year FFBP of 45% [95% CI 32-59] vs 71% [95% CI 64-78] in low-intermediate GC. Similar estimates for GC risk groups were observed in the 64Gy vs 70Gy in GC high (5-year FFBP of 51% [95% CI 32-70] vs 39% [95% CI 20-59]) and in low-intermediate GC (75% [95% CI 65-84] vs 69% [95% CI 59-78]). Conclusions: This study represents the first contemporary randomized controlled trial in patients with recurrent prostate cancer treated with early SRT without ADT that has validated the prognostic utility of the GC. Independent of standard clinicopathologic variables and radiotherapy dose, patients with a high-GC were more than twice as likely than a lower GC score to experience biochemical and clinical progression and receive salvage ADT. This data confirms the clinical value of Decipher GC for tailoring treatment in the postoperative salvage setting.

A phase 3, multicenter, randomized study evaluating the efficacy of TAR-200 in combination with cetrelimab versus concurrent chemoradiotherapy in participants with muscle-invasive urothelial carcinoma of the bladder

TPS4586

Background: The standard of care for patients with muscle-invasive bladder cancer (MIBC) consists of neoadjuvant chemotherapy and radical cystectomy (RC) or chemoradiotherapy (CRT). However, RC is associated with potential morbidity or mortality from the procedure. TAR-200 is an intravesical drug-delivery system designed for the local continuous release of gemcitabine within the bladder. Cetrelimab is an investigational immunoglobulin G4 anti–programmed cell death protein-1 antibody. In patients with MIBC, this clinical trial will evaluate whether combination treatment with intravesical TAR-200 and systemic cetrelimab will result in enhanced local and systemic antitumor activity versus concurrent CRT. Methods: SunRISe-2 (NCT04658862) is a prospective, multicenter, open-label, randomized phase 3 study evaluating the efficacy and safety of intravesical TAR-200 plus systemic cetrelimab versus CRT in participants with MIBC. Eligible participants are aged ³18 years with an ECOG performance status of 0, 1, or 2, and histologically proven, cT2-T4a, N0, M0 urothelial carcinoma of the bladder diagnosed within 90 days of the randomization date, and who refuse or are ineligible for RC. Approximately 550 participants will be randomized in a 1:1 ratio and with stratification by 2 factors: transurethral resection of bladder tumor screening results (visibly complete vs incomplete) and screening tumor stage (T0 vs Ta/T1/Tis vs T2-T4a). Participants in Arm 1 will receive intravesical TAR-200 every 3 weeks for the first 18 weeks on study; and, beginning at week 24, every 12 weeks through study year 3. Cetrelimab will be dosed every 3 weeks until month 18. Participants in Arm 2 will receive standard of care CRT (with either cisplatin or gemcitabine, for up to 6 weeks). A primary disease assessment will be performed at week 18 to evaluate treatment response in both arms. Subsequent assessments (axial imaging and cystoscopy) will occur at week 24 and every 12 weeks thereafter through study year 2, and then every 24 weeks through study year 5. The primary endpoint is bladder intact event-free survival. Key secondary endpoints include metastasis-free survival, overall survival, overall response rate (at week 18), and safety and tolerability. Other/exploratory end points include assessments of cancer-specific survival, time to symptomatic progression, pharmacokinetics, immunogenicity, health-related quality of life, healthcare resource utilization, and biomarkers. Participants are being enrolled at approximately 272 study sites worldwide. The study opened for enrollment in December 2020. Clinical trial information: NCT04658862.

Interim results of aasur: A single arm, multi-center phase 2 trial of apalutamide (A) + abiraterone acetate + prednisone (AA+P) + leuprolide with stereotactic ultra-hypofractionated radiation (UHRT) in very high risk (VHR), node negative (N0) prostate cancer (PCa)

5012

Background: Standard of care in VHR PCa is radiation therapy (RT) with 18-36 months (mos) of androgen-deprivation therapy (ADT). With this regimen, chronic ADT toxicity is significant and biochemical recurrence (BCR) frequent. We sought to improve tumor control and minimize toxicity with intensified short course ADT with dual androgen receptor signaling inhibitors (ARSI) and UHRT. Methods: 64 patients (pts) with VHR, N0 PCa were enrolled from 4 centers. VHR PCa was defined as Gleason score (GS) 9-10, >4 cores of GS 8 disease, or 2 high-risk features (including rT3/T4 disease). Treatment (tx) involved 6 mos of A, AA+P, and leuprolide with prostate/seminal vesicle-directed RT (7.5-8 Gy x 5 fractions). The primary endpoint was BCR defined as nadir PSA + 2ng/mL. Biochemical recurrence-free survival (bRFS) is reported herein. Our hypothesized reduction in BCR from 25% to 10% at 3 years (yrs) required 53 pts to provide a power of 0.84 and an alpha of 0.03. Undetectable PSA was defined as <0.10 ng/mL. Non-castrate testosterone (T) was a post-tx value >150 ng/mL. All analyses were intention-to-treat. Toxicity and health-related quality of life measures were evaluated using CTCAEv4.0 and the EPIC-26 questionnaire. Results: Baseline characteristics are summarized in the Table; 63 of 64 pts completed protocol tx. Median time to nadir PSA from tx start was 2 mos (range, 1-9); 63 of 64 pts (98.4%) achieved an undetectable nadir PSA. Median time to post-tx, non-castrate T was 6.5 mos (range, 2.5-25.5). Median follow-up (f/u) for pts without BCR was 30 mos (range, 15-44). Seven pts had BCR; 2-yr bRFS was 95.0% (95% CI, 89.7-100); 3-yr bRFS was 89.7% (95 CI, 81.0-99.3). For the 57 pts without BCR, 56 (98.2%) had T > 150ng/mL at last f/u; median PSA at last f/u was 0.10 ng/mL (IQR, <0.10-0.30); of these, 40 (70.2%) pts had PSAs ≤ 0.20 ng/mL with 24 (42.1%) undetectable. Fifteen pts experienced transient Grade 3 toxicities: 12 (18.8%) with hypertension and 3 with rash (4.7%). EPIC-26 scores for a subset of pts (n=21) at baseline and 12 mos showed no significant decline in urinary or bowel domains; declines in sexual (-11.9) and hormone (-5.7) domains met significance. Conclusions: Compared to historic controls with the long course ADT, AASUR demonstrated impressive 3-yr bRFS, rapid T recovery, and limited toxicities; the safety profile of this regimen was consistent with the known AE profile of the ARSI and RT. This regimen warrants further, randomized evaluation. Funded by Janssen Pharmaceuticals. Managed by the Prostate Cancer Clinical Trials Consortium. Clinical trial information: NCT02772588. [Table: see text]

Prospective randomized trial of gene expression classifier utility following radical prostatectomy (G-MINOR)

15

Background: Decipher is a tissue-based genomic classifier (GC) developed and validated in the post-radical prostatectomy (RP) setting as a predictor of metastasis. We conducted the first prospective randomized controlled trial assessing the use of a prostate cancer GC, with a primary objective to determine the impact of test results on adjuvant treatment decisions. Methods: The Genomics in Michigan ImpactiNg Observation or Radiation (G-MINOR) randomized trial enrolled participants across 12 centers between January 2017-August 2018. Eligible patients had undergone RP within 9 months of enrollment, had pT3-4 disease and/or positive surgical margins, and a PSA < 0.1ng/mL. Patients were assigned to either the GC or Usual Care (UC) group using cluster-crossover block randomization. Patients and providers in both arms received a CAPRA-S recurrence risk score. Decipher scores were obtained on RP tissue of all patients, but patients and providers in the UC arm were blinded to the results. The primary endpoint was the impact of impact of GC test result on adjuvant treatment decisions compared to clinical factors alone within 18 months of RP. Results: 356 patients were randomized and 340 had at least 18 months of follow-up. Of these, all but 2 control (UC) patients had sufficient tissue to pass quality control for GC testing. Randomization resulted in 175 (51.5%) GC and 165 (48.5%) UC patients. There were no significant differences in clinical variables or Decipher scores between arms. At 18 months post-RP, 19 (10.9%) patients in the GC group and 12 (7.3%) patients in the UC group had received adjuvant treatment. In the primary analysis, availability of the GC score in the GC arm was significantly associated with adjuvant treatment in GC high-risk patients after controlling for CAPRA-S risk (OR 7.6, 95%CI 1.95-29.6, p = 0.009). In the GC arm, both GC score (OR 8.8, 95%CI 1.9-39.7, p = 0.005) and CAPRA-S score (OR 3.8, 95%CI 1.09-12.9, p = 0.04) were independently associated with adjuvant treatment in a multivariable logistic regression model. Conclusions: In the first ever randomized trial testing the impact of a prostate cancer genomic classifier on treatment decisions, the use of a GC post-RP impacted post-operative treatment in a manner concordant with classifier risk. Further follow-up will be necessary to assess the impact of GC testing on oncologic outcomes. Clinical trial information: NCT02783950. [Table: see text]

Factors influencing noncompletion of radiotherapy among men with localized prostate cancer

199

Background: Treatment non-completion may occur with radiotherapy (RT), especially with protracted treatment courses such as RT for prostate cancer, and may affect the efficacy of RT. For men with localized prostate cancer managed with primary RT, we evaluated associations between rates of treatment non-completion and RT fractionation schedules. Methods: The National Cancer Database identified men diagnosed from 2004-2014 treated with primary RT. Patients receiving 180cGy/fraction (conventional), 200cGy/fraction (conventional), 250cGy/fraction (moderate hypofractionation), and 300cGy/fraction (moderate hypofractionation) were defined as having completed radiotherapy if they received ≥40 fractions, ≥37 fractions, ≥28 fractions, and ≥19 fractions, respectively. Stereotactic body radiotherapy (SBRT) was defined as 5-8 fractions of 600-800cGy/fraction. Odds ratios compared rates of treatment noncompletion, adjusting for various sociodemographic covariates. Propensity-adjusted multivariable Cox regression assessed the association between treatment completion and overall survival. Results: Of 93,079 patients, 90.5% (N = 84,260) received conventional fractionation, 2.3% (N = 2,181) received moderate hypofractionation, and 7.1% (N = 6,638) received SBRT. Rates of non-completion were 10.0% (N = 8,406) among patients who received conventional fractionation, 7.5% (N = 163) among patients who received moderate hypofractionation, and 1.7% (N = 115) among patients who received SBRT (OR versus conventional: 0.214, 95%CI 0.177-0.258, P < 0.001). The rate of non-completion among 15,417 African American patients was 11.8%, compared to 8.8% among 74,189 white patients (OR 1.39, 95%CI 1.31-1.47, P < 0.001). On subgroup analysis, the disparity in non-completion persisted for conventional fractionation (12.4% vs. 9.4%, OR 1.36, 95%CI 1.29-1.44, P < 0.001) and moderate hypofractionation (13.6% vs. 6.6%, OR 2.24, 95%CI 1.52-3.29, P < 0.001), but not for SBRT (2.0% vs. 1.6%, OR 1.25, 95%CI 0.76-2.06, P = 0.384). Non-completion was associated with worse survival on propensity-adjusted multivariate analysis (HR 1.37, 95%CI 1.31-1.43, P < 0.001). Conclusions: SBRT was associated with lower rates of RT non-completion among men with localized prostate cancer. African American race was associated with greater rates of treatment non-completion, although the disparity may be decreased among men receiving SBRT.

MR1 in combination with tumor mutational burden and PD-1/PD-L1 expression as a potentially novel clinical predictor for T cell exhaustion and immune checkpoint inhibitor response

3109

Background: Immune checkpoint inhibitors (ICIs) restore T cell function by reversing T cell exhaustion. Variable response to ICIs warrants the development of precise predictive biomarkers, which is challenging due to difficulty in capturing the interplay of factors involved with tumor cell immune recognition. High intratumoral expression of MR1, the MHC-I related protein basally expressed on cancer cells, may drive T cell exhaustion through presentation of cancer-specific antigens. Here, we construct a database to study the relationship between MR1, tumor mutational burden (TMB), the PD-1/PD-L1 axis and T cell exhaustion across 8,975 sequenced tumors and 27 cancer types. Methods: RNA Seq by expectation maximization (RSEM) values from the TCGA were collected and normalized along with expression data for markers of interest (Table). TMB was defined as the number of non-synonymous somatic mutations per sample. For each cancer, 5 cohorts were created based on ascending mean expression levels of MR1, PD-1, PD-L1, and increasing TMB. For each cancer, an “immunogenicity score” for these factors was computed, and its relationship with T cell exhaustion signatures was assessed via linear regression. Data is presented as adjusted R2 and p-value. Results: While PD-1 and T cell exhaustion marker expression were correlated across cancers, the “immunogenicity score” (IS) correlated with exhaustion markers specifically in cancers with FDA-approved ICIs. Excluding MR1 from the score weakened the correlation with EOMES and TBET expression (Table). Each component of the score analyzed independently failed to show a statistically significant correlation for both EOMES and TBET expression. Conclusions: In this cross-cancer analysis, we support the hypothesis that presentation of metabolic intermediates in cancer cells via MR1 may drive T cell exhaustion. Also, the novel “immunogenicity score”, which incorporates MR1 into standard biomarkers for response to ICIs may convey the global picture of cancer cell recognition by the immune system and warrants further investigation as a tool for predicting clinical response. [Table: see text]

Short-term adjuvant versus neoadjuvant hormone therapy in localized prostate cancer: A pooled individual patient analysis of two phase III trials

5584

Background: The timing of systemic therapy in relation to radiotherapy (RT) is important in most malignancies. In contrast, androgen deprivation therapy (ADT) has largely been investigated in relation to its duration rather than its sequencing with RT. Herein, we conduct the first combined individual patient analysis of two phase III randomized trials to determine the optimal timing of ADT with RT in localized prostate cancer (PCa). Methods: Individual patient data was obtained from the Malone et al trial (JCO 2019), which randomized patients to receive neoadjuvant/concurrent or concurrent/adjuvant ADT for 6 months with prostate only RT. This was combined with the prostate only RT arms of RTOG 9413 that randomized patients to 4 months of neoadjuvant/concurrent or adjuvant ADT. The neoadjuvant/concurrent arms of both trials were combined into the “neoadjuvant” group, and the concurrent/adjuvant (Malone) and adjuvant arm (RTOG 9413) were combined in the “adjuvant” group. The Kaplan-Meier method was used to estimate overall survival (OS) and progression-free survival (PFS). Cumulative incidence of distant metastasis (DM), PCa-specific mortality (PCSM) and biochemical failure (BF) were calculated using the Fine-Gray method with non-PCa deaths as competing events. Late genitourinary (GU) and gastrointestinal (GI) toxicity are also reported. Results: The median follow-up was 14.9 years (yrs) and 1065 patients were included (n=531 neoadjuvant, 534 adjuvant). Groups were well balanced for all baseline characteristics. Adjuvant ADT was superior to neoadjuvant ADT in terms of BF (15yr: 33% vs 43%, HR: 1.37 (95%CI: 1.12-1.68), p=0.002), DM (15yr: 12% vs 18%, HR: 1.40 (95%CI: 1.00-1.95), p=0.04), and PFS (15yr: 36% vs 29%, HR: 1.25 (95%CI: 1.07-1.47), p=0.01). Adjuvant ADT yielded lower PCSM (15yr: 15% vs 20%, HR: 1.29 (95%CI: 0.95-1.75), p=0.10), but did not reach statistical significance. This approached statistical significance in high risk PCa (HR 1.39 (95%CI 1.00-1.93), p=0.053). OS was not significantly different between arms (15yr: 39% vs 34%, HR: 1.11 (95%CI: 0.95-1.30), p=0.20). There was no significant difference in either late grade ≥3 GI (p=0.21) or GU (p=0.98) toxicity. Conclusions: We demonstrate for the first time that sequencing of ADT with RT significantly impacts long-term oncologic outcomes in localized PCa, favoring an adjuvant rather than neoadjuvant approach, without increasing late toxicity. This data has important implications to ongoing and future clinical trial design. Clinical trial information: NCT00769548 .

DCE-MRI Evaluation of 10 patients with brain metastases treated with RRx-001, a Myc inhibitor and a CD47 and PD-L1 downregulator, in a phase I/II trial called BRAINSTORM

e14509

Background: In a Phase 1/2 trial called BRAINSTORM (NCT02215512) for brain metastases from any histology, quantitative changes in perfusion MRI after administration of RRx-001, a mic inhibitor and CD47 and PD-L1 downregulator with vascular normalizing properties, were determined and correlated with response. Methods: Ten patients with 64 total lesions evaluable at baseline, 24 hours, and end of radiotherapy (RT) that participated in BRAINSTORM were subjected to a correlative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) examination four days prior to the start of whole brain radiotherapy (WBRT) that evaluated Ktrans (capillary permeability) and Vp (plasma volume). The treatment comprised RRx-001 on Day -4, pre-WBRT then twice weekly during WBRT. Four dose levels were administered (5 mg/m2, 8.4 mg/m2, 16.5 mg/m2, and 27.5 mg/m2. Results: 10 patients underwent DCE-MRI scans and eight patients with 44 total evaluable lesions had available imaging at 1 month, and 6 patients with 29 total evaluable lesions had imaging at 4 months. On univariate analysis, only a decrease in 24-hour Vp from baseline after a single dose of RRx-001 was marginally associated with absolute tumor volume response 1 month after treatment (p-0.07). In a multivariate model, only Vp prior to therapy and 24-hour change in Vp were retained in the model after stepwise selection. A reduction in Vp 24 hours after RRx-001 (prior to WBRT) was associated with reduced tumor volume at 1 month (Estimate 0.88, 95% CI 0.37-1.40, p = 0.001) and 4 months (Estimate 1.51, 95% CI 0.58-2.43, p = 0.003). Likewise, a lower Vp prior to therapy was associated with reduced tumor volume at 1 month (Estimate 0.73, 95% CI 0.29-1.17, p = 0.002) and 4 months (Estimate 1.8, 95% CI 0.95-2.65, p = 0.0002), suggesting anti-angiogenic activity and early potential vascular normalization after a single dose of RRx-001 predictive of longer-term tumor response. Conclusions: RRx-001 induced a reduction in blood plasma volume, which was associated with tumor response and which suggests a vascular normalizing effect that merits further investigation in future planned studies. Clinical trial information: NCT02215512.

Differential expression of PSMA and 18F-fluciclovine transporter genes in metastatic castrate-resistant and treatment-emergent small cell/neuroendocrine prostate cancer

24

Background: 18F-fluciclovine (Axumin) PET/CT imaging is recommended by the NCCN in the setting of biochemical recurrence, while prostate-specific membrane antigen (PSMA) PET/CT is preferred by the EAU. The utility of these methods in the post-androgen deprivation therapy (ADT) setting however, is less defined. Our objective was to compare relative gene expression of the molecular targets of these imaging modalities— fluciclovine transporter genes (LAT1-4, ASCT1-2) and PSMA—in metastatic castrate resistant prostate cancer (mCRPC) and treatment-emergent small cell/neuroendocrine prostate cancer (t-SCNC). Methods: Genome-wide expression profiles of five mCRPC cohorts (Aggarwal, Grasso, Kumar, Beltran, Robinson, et al) were used to characterize relative expression of fluciclovine transporter (LAT1-4, ASC1-2) and PSMA (FOLH1) genes. 3 cohorts (Kumar, Beltran, Aggarwal) were enriched with t-SCNC tumors. The GSE35988 cohort included primary tumors and mCRPC. RNA expression profiling methods were consistent within cohorts. Results: 518 mCRPC specimens were included. In the GSE35988 cohort, PSMA expression was downregulated in mCRPC when compared to primary localized tumors (p=0.01). PSMA expression was further depressed in t-SCNC when compared with mCRPC (p<0.001). Of the fluciclovine transporter genes, LAT1 and LAT4 were overexpressed in mCRPC when compared to primary tumors, while ASC2 was less expressed (p<0.001). LAT1 was further overexpressed in t-SCNC when compared to mCRPC, while LAT2 was less expressed (p<0.001). PSMA expression was negatively correlated with LAT1 (p<0.001) but positively correlated with LAT2 (p=0.006). Other fluciclovine transporters were not correlated. Conclusions: Expression of PSMA and a subset of fluciclovine transporter genes are inversely correlated in mCRPC and t-SCNC. These findings suggest that fluciclovine-based imaging may play a role in castrate resistant states. Clinical comparison between PSMA- and fluciclovine-based imaging modalities in mCRPC and t-SCNC is warranted.

Utilization of androgen deprivation therapy (ADT) and stereotactic body radiation therapy (SBRT) for localized prostate cancer (PC) in the United States (US)

370

Background: Randomized trials have demonstrated improved survival with the addition of ADT to conventionally fractionated radiotherapy (RT) for men with unfavorable intermediate risk (UIR) and high-risk (HR) prostate cancer (PC). The benefit of ADT with SBRT is unknown. The purpose of this study is to examine ADT utilization with SBRT in the US. Methods: Men > 40 years old with localized PC treated with external beam RT for curative intent between 2004-2015 were analyzed from the National Cancer Database. Patients who received brachytherapy, surgery, or lacked ADT or risk stratification data were excluded. A total of 7,559 men treated with SBRT (≥5Gy/fraction; ≤5 fractions; dose ≥25Gy) versus 133,825 men treated with moderate or conventional RT (≤3Gy/fraction; dose ≥60Gy) were included. Patients were stratified by risk: low (LR), favorable intermediate (FIR), UIR, and HR using NCCN criteria. Differences between RT and SBRT were determined via Chi-square test. Results: Among all PC treated with RT, SBRT use increased from 2004 to 2015 across risk groups – overall: 0.9% to 10.3%; LR: 0.9% to 21.6%; FIR: 1.1% to 13.7%; UIR: 0.6% to 10.8%; HR: 0.8% to 2.8%; p < 0.001. Among all PC treated with RT, ADT use declined from 2004 to 2015 for LR (22.8% to 5.5%), FIR (51.7% to 40.0%), UIR (53.4% to 49.5%), but not HR (78.9% to 84.2%); p < 0.001. Patients with EBRT were more likely to receive ADT compared to those with SBRT across risk groups (Table). Conclusions: The majority of patients receiving SBRT for UIR and HR disease in the US do not receive concurrent ADT, despite national guideline recommendations and the lack of level 1 evidence to support this practice pattern. The omission of ADT may result in inferior oncologic outcomes, and randomized trials are needed to establish the safety of omitting ADT with SBRT for higher risk PC.[Table: see text]

Cost-effectiveness of upfront therapeutic options in low-volume de novo metastatic hormone-sensitive prostate cancer

211

Background: Low-volume de novo metastatic hormone-sensitive prostate cancer (mHSPC) has historically been treated with lifelong androgen deprivation therapy (ADT). Recently, however, the addition of several advanced therapeutic options – radiation therapy (RT) to the primary, advanced hormonal therapy agents such as abiraterone acetate/prednisone (AAP), and chemotherapy – to ADT have been shown to improve survival in low-volume mHSPC. The objective of this study was to compare the cost-effectiveness of treating low-volume mHSPC patients upfront with RT+ADT, AAP+ADT, or docetaxel+ADT. Methods: A Markov-based cost-effectiveness analysis was constructed comparing three treatment strategies for low-volume mHSPC patients: (1) upfront RT+ADT --> salvage AAP+ADT --> salvage docetaxel+ADT; (2) upfront AAP+ADT --> salvage docetaxel+ADT, and (3) upfront docetaxel+ADT --> salvage AAP+ADT. Transition probabilities were calculated using data from STAMPEDE arms C/G/H, COU-AA-301, COU-AA-302, and TAX-327. RT was delivered via five-fraction stereotactic body radiation therapy. The analysis utilized a 10-year time horizon, and a $100,000/quality adjusted life year (QALY) willingness-to-pay threshold. Utilities were extracted from the literature; costs were taken from Medicare fee schedules and VA oral drug contracts. Results: At 10 years, total cost was $140K, $259K, and $189K, with total QALYs of 4.66, 5.03, and 3.72 for strategies (1) upfront RT+ADT, (2) upfront AAP+ADT, and (3) upfront docetaxel+ADT, respectively. Compared to upfront RT+ADT, upfront AAP+ADT was not cost-effective (ICER: $321K/QALY). This result remained unchanged even after modification of various model inputs in 1-way sensitivity analysis. Upfront docetaxel+ADT was both more costly and less effective than upfront RT+ADT (ICER: -$53K/QALY). Conclusions: At 10 years, RT+ADT is cost-effective compared to other advanced systemic therapy options alone, and should be considered as a viable treatment strategy in all patients with a low-burden of metastatic disease. Additional studies are needed to determine whether any benefit exists in combining RT to the primary with upfront advanced systemic therapy.

Clinical-genomic sub-classification of high-risk prostate cancer: Implications for tailoring therapy and clinical trial design

337

Background: Current risk stratification schema have limited prognostic performance in predicting outcome within National Comprehensive Cancer Network (NCCN) high-risk to very high-risk prostate cancer. Methods: Two multicenter high-risk cohorts were used for training (n = 214) and validation (n = 151) of a novel RNA microarray-based integrated clinical-genomic Classifier Optimized for Outcome in High-risk Prostate cancer (COOHP) to classify patients as COOHP favorable high-risk, standard high-risk, or very high-risk. Cox analysis was used to model metastasis-free survival (MFS), prostate cancer-specific survival (PCSS), and overall survival (OS). Model performance was compared to prior sub-classification systems using time-dependent c-indices. Results: Among NCCN high/very high-risk patients in the training cohort, 11% were classified as COOHP favorable high-risk, 70% as COOHP standard high-risk, and 18% as COOHP very high-risk. Patients with COOHP favorable high-risk disease had better rates of 5-year MFS compared to those with COOHP standard high-risk disease (94% vs 76%, hazard ratio [HR] 0.10, p = 0.02), and patients with COOHP very high-risk disease had worse 5-year MFS compared to those with COOHP standard high-risk disease (34% vs 76%, HR 3.5, p < 0.0001). Similarly, patients with COOHP very high-risk disease had worse 10-year PCSS compared to those with COOHP standard high-risk disease (36% vs 82%, HR 4.4, p < 0.0001). The c-indices for 5-year MFS and 10-year PCSS in the training cohort were 0.80 and 0.74, significantly improved compared to prior clinical and clinical-genomic risk stratification systems (0.62-0.69 for 5-year MFS and 0.56-0.63 for 10-year PCSS). These results were consistent in the validation cohort, where 5-year MFS significantly varied among the three COOHP subgroups (100% vs 89% vs 79%, p = 0.020), as did 10-year OS (100% vs 71% vs 53%, p = .040). Conclusions: A clinical-genomic risk stratification system specifically designed to discriminate prognosis in high-risk prostate cancer better identified favorable high-risk and very high-risk subsets of disease compared to prior clinical and clinical-genomic stratification systems.

Characterization of PSMA and 18F-fluciclovine transporter gene expression in localized prostate cancer

295

Background: While 18F-fluciclovine PET/CT is approved in the US and recommended by the NCCN, prostate-specific membrane antigen (PSMA) PET/CT is more common in Europe/Australia and recommended by the EAU. Less is known about the biology of lesions detected by either modality. 18F-fluciclovine PET relies on radiotracer uptake by amino acid transporters LAT1-4 and ASCT1-2. PSMA PET is dependent on surface expression of PSMA. We compared relative expression of PSMA and fluciclovine transporter genes in radical prostatectomy (RP) samples to determine their distribution across subtypes and correlation with outcomes. Methods: Gene expression data of 19,102 RP samples were analyzed using the Affymetrix Human Exon 1.0 ST microarray. 1,135 patients had long term follow up. Associations between expression of PSMA and fluciclovine transporter genes (LAT1-4 and ASCT1-2) and pathologic variables, molecular subtypes, and clinical outcomes were conducted. Results: All fluciclovine transporter genes (LAT 1-4, ASCT1-2) were expressed at lower levels than PSMA (p <0.0001). PSMA expression was positively correlated with genomic risk score and pathologic Gleason score (p<0.0001), but LAT2-3 and ASCT2 were inversely correlated with genomic risk in primary tumors (p<0.0001) and less expressed in GS 9-10 tumors (p<0.0001). PSMA expression was associated with worse metastasis-free survival (MFS) (HR 1.45, p=0.001) and lymph node involvement (HR 2.14, p<0.0001). Expression of LAT2, LAT3, ASCT2 expression was associated with better MFS (HR 0.85, 0.63, 0.74, p<0.0001-0.04). After multivariable adjustment, PSMA expression remained independently prognostic of poorer MFS (HR 1.3, p=0.028). Luminal B subtype was notable for PSMA overexpression; Luminal A was enriched in ASCT2 and LAT2 (p<0.0001). PSMA expression did not correlate with ERG fusion prostate cancers, but LAT2, ASCT1, and ASCT2 were overexpressed in ERG fusion negative tumors (p<0.0001). Conclusions: PSMA expression is associated with more aggressive disease and poorer clinical outcomes than fluciclovine transporter genes in localized prostate cancer. Molecular subtypes of prostate cancer vary in PSMA and fluciclovine transporter gene expression.

Impact of initial treatment selection on clinical outcomes after biochemical failure in radiorecurrent high-risk prostate cancer

208

Background: Treatment of high risk prostate cancer (HRPCa) with external beam radiotherapy (EBRT) plus brachytherapy (BT) boost (EBRT+BT) has been prospectively associated with lower rates of BCR, albeit potentially with increased toxicity, and retrospectively linked to decreased distant metastasis (DM) and PCa-specific mortality (PCSM) compared to EBRT alone. However, it is unclear whether patients who develop BCR following either approach have similar downstream oncologic outcomes. Methods: We identified 706 out of 3820 men with HRPCa treated at 13 institutions from 1998-2015 with EBRT (n=468/2134) or EBRT+BT (n=238/1686) who developed BCR. We compared rates of DM, PCSM, and all-cause mortality (ACM) after BCR between treatment groups using Fine-Gray competing risk regression. Models were adjusted for age, Gleason grade group, initial PSA (iPSA), clinical T stage, time-dependent use of systemic salvage, and interval to BCR using inverse probability of treatment weighting. Results: Median follow-up was 9.9 years from RT and 4.8 years from BCR. Groups were similar in age, iPSA, presence of ≥2 HR features, and median interval to BCR (3.3 years). Most men received neoadjuvant/concurrent androgen deprivation therapy (ADT), 92.5% and 91.0% for EBRT and EBRT+BT, respectively, though for a longer duration with EBRT (median 14.7 vs. 9.0 months, p=0.0012). Local and systemic salvage rates were 2.3% and 36.3% after EBRT, and 2.6% and 43.6% after EBRT+BT, respectively. Initial EBRT+BT was associated with significantly lower rates of DM after BCR (HR 0.48, 95% CI 0.36-0.64, p<0.001). Rates of PCSM and ACM did not significantly differ (HR 0.93, 95% CI 0.67-1.30, p=0.93, and HR 0.8, 95% CI 0.6-1.1, p=0.11, respectively). Conclusions: In this large retrospective series of radiorecurrent HRPCa, initial treatment with EBRT+BT was associated with significantly lower rates of DM after BCR compared with EBRT, despite shorter ADT use and a similar median interval to BCR. Local salvage was widely underutilized in both groups. In the absence of salvage for local failure after EBRT, upfront treatment intensification with BT may reduce DM, though not PCSM or ACM, even after development of BCR.

Association of black race with improved outcomes following definitive radiotherapy with androgen deprivation therapy for high-risk prostate cancer: A meta-analysis of eight randomized trials

327

Background: Though Black men with prostate cancer are more likely to have aggressive disease features than White men, race-specific differences in initial treatment responses in localized disease remains unknown. Methods: Individual patient data were obtained for 9259 patients (including 1674 [18.1%] Black men and 7585 [81.9%] White men) enrolled on eight randomized controlled trials evaluating definitive radiotherapy (RT) ± short-term or long-term androgen deprivation therapy (STADT and LTADT). The primary endpoints were biochemical recurrence (BCR), distant metastasis (DM), and prostate cancer-specific mortality (PCSM). Fine-Gray subdistribution HR (sHR) models were developed to evaluate the cumulative incidences of all endpoints after stratification by National Comprehensive Cancer Network risk grouping. A meta-analysis was done to estimate pair-wise comparisons of treatments within and between Black and White men, after adjusting for age, Gleason score, clinical T stage, and initial PSA. Results: Black men were more likely to have NCCN high-risk disease at enrollment (656/1674 [39.2%] vs 2506/7585 [33%], p<0.001). However, within the high-risk stratum Black men had lower 10-year rates of BCR (46.1% vs. 50.4%, p=0.02), DM (14% vs. 21.6%, p<0.001), and PCSM (4.9% vs. 9.8%, p<0.001). After adjusting for age and disease characteristics, Black men with high-risk prostate receiving RT+STADT had lower rates of BCR (sHR 0.73, 95% CI 0.62-0.86, p<0.001), DM (sHR 0.64, 95% CI 0.49-0.84, p=0.001) and PCSM (sHR 0.49, 95% CI 0.25-0.95, p=0.04). There were no differences in BCR, DM, or PCSM among men receiving RT+LTADT. The interaction between race and the impact of adding STADT to RT alone on BCR was statistically significant (p=0.003). Conclusions: Black men enrolled on randomized trials with long-term follow-up have higher risk disease at enrollment, but have better BCR, DM, and PCSM outcomes with RT-based therapy compared with White men, particularly with the addition of STADT.

Prostate oncologic therapy while ensuring neurovascular conservation (POTEN-C): A phase II randomized controlled trial of stereotactic ablative body radiotherapy (SAbR) with or without neurovascular sparing for erectile function preservation in localized prostate cancer

TPS381

Background: Radiotherapy (RT) associated sexual dysfunction occurs in half of men following treatment for localized prostate cancer. Proposed mechanisms include vascular injury of adjacent internal pudendal arteries (IPA), penile bulb (PB), corpora cavernosa (CC) or neurovascular bundles (NVB). Ability to spare these structures has been limited by a presumed need to treat the entire prostate gland, while also preventing rectal injury. Recent innovations have challenged this issue: a) precise dose delivery with stereotactic ablative RT (SAbR), b) improved spatial mapping of clinically significant disease with mpMRI, c) rectal avoidance with rectal spacer use. Methods: POTEN-C is a multi-center phase II randomized control trial, which includes men with a) low-intermediate risk prostate cancer eligible for SAbR without ADT, b) potent by sexual composite score ≥60 on EPIC patient-reported quality of life instrument, c) mpMRI delineated disease (PIRADS v2 score 3-5) ≥5mm to at least one ‘spared’ NVB. After placement of rectal spacer gel and CT/MRI simulation, men are randomized to standard SAbR to 40-45Gy/5fx or neurovascular-sparing SAbR. In the sparing experimental arm, the prostate PTV is given 30Gy/5fx excluding unilateral ‘spared’ NVB, while a 40-45Gy PTV further excludes a 5mm protective shell on the unilateral ‘spared’ NVB+IPA+PB+CC. Centralized rapid review of initial contours/plans and online training materials are integrated. The primary endpoint is 2-year patient-reported potency, measured by EPIC sexual composite score. We hypothesize that neurovascular sparing SAbR will reduce 2-year EPIC score decline from a control of 20 to 10 (corresponding to a MCID). Assuming standard deviation 20, two-sided significance level 0.10 with two-sample t-testing, and 15% attrition, we intend to enroll 120 patients to provide 80% power to detect this difference. Secondary endpoints include sexual medication/aid use, relapse rates, GU/GI toxicity. Enrollment is ongoing. Details: http://www.poten-c.org . Clinical trial information: 03525262.

Transcriptome profiling of NRG Oncology/RTOG 9601: Validation of a prognostic genomic classifier in salvage radiotherapy prostate cancer patients from a prospective randomized trial

276

Background: Decipher is a genomic classifier (GC) that estimates risk of prostate cancer (PCa) distant metastases (DM) post-radical prostatectomy (RP). Herein, we validate the GC within the context of a randomized phase 3 trial. Methods: RP specimens from patients on the NRG/RTOG 9601 phase 3 placebo-controlled randomized trial of salvage radiotherapy (sRT) +/- 2 years of bicalutamide (NCT00002874) were centrally reviewed and the highest-grade tumor underwent RNA extraction. Samples passing quality control (QC) were run on a clinical-grade whole-transcriptome assay to assign the GC score (scale 0-1). Our NCTN-CCSC approved pre-specified statistical plan (NRG-GU-TS002 CSC0075) included the primary objective of validating the ability of the GC to independently prognosticate the cumulative incidence of DM, with secondary endpoints of prostate cancer-specific mortality (PCSM) and overall survival (OS). Results: Of patients with tissue available, 352 passed QC and were included for analysis. The final GC cohort was a representative sample of the overall cohort, with a median follow-up of 13 years. On multivariable analysis, the GC (continuous variable) was independently associated with DM (HR 1.19 [95%CI 1.06-1.35], p=0.003), PCSM (HR 1.37 [95%CI 1.18-1.61], p<0.001), and OS (HR 1.16 [95%CI 1.06-1.28], p=0.002) after adjusting for age, race, Gleason score, T-stage, margin status, entry PSA, and treatment arm. The estimated absolute impact of bicalutamide on 12-year OS was less in patients with lower vs higher GC scores (2.4% vs 8.9%), further demonstrated in men receiving early sRT at PSA <0.7 ng/mL (-2.0% vs 5.0%). Conclusions: This is the first validation of this GC in a prospective randomized trial cohort and demonstrates association of the GC with DM and PCSM independent of standard clinicopathologic variables. The GC may help personalize shared decision-making to weigh the absolute benefit from the addition of bicalutamide to sRT.