Detection Rate of 18F-rhPSMA-7.3 PET in Patients with Suspected Prostate Cancer Recurrence at PSA Levels <1 ng/mL: Data from the Phase 3 SPOTLIGHT Study

PURPOSE/OBJECTIVE(S)

Novel molecular imaging agents yield potential for localization of disease in patients with biochemical recurrence of prostate cancer when PSA levels are still low, and may facilitate early intervention with selective therapy to optimize outcomes. Radiohybrid (rh) positron emission tomography (PET) radiopharmaceutical, 18F-rhPSMA-7.3, is a novel high affinity prostate-specific membrane antigen (PSMA)-targeting ligand with potential for low bladder activity. The SPOTLIGHT study (NCT04186845) evaluated the diagnostic performance of 18F-rhPSMA-7.3 in men with suspected prostate cancer recurrence. Here, we report findings from a post-hoc analysis of SPOTLIGHT data, which determined the 18F-rhPSMA-7.3 detection rates (DR) at low-very low PSA levels.

MATERIALS/METHODS

Patients enrolled in SPOTLIGHT underwent PET 50-70 min after IV administration of 296 MBq 18F-rhPSMA-7.3. Scans were evaluated by 3 blinded central readers, with the majority read representing agreement between ≥2 independent readers. For the present analysis, all patients with an evaluable 18F-rhPSMA-7.3 PET and who had a baseline PSA <1 ng/mL were selected. Overall (patient-level) and regional DR by majority read were determined, stratifying DR according to the patients' baseline PSA level (<0.2, ≥0.2 - <0.3, ≥0.3 - <0.5, and ≥0.5 - <1 ng/mL).

RESULTS

In total, 389 patients (median [range] PSA, 1.10 [0.03-135] ng/mL, 84 with intact prostate) had an evaluable 18F-rhPSMA-7.3 scan. The overall DR was 83% (322/389) by majority read. Of the 389 patients with an evaluable 18F-rhPSMA-7.3 scan, 188 had a baseline PSA <1 ng/mL and were eligible for the present analysis. Despite low patient numbers in some PSA categories, moderate to high DR were observed, with the patient-level DR shown to increase with increasing baseline PSA (see table). Overall, 68% (128/188) of patients with a PSA <1 ng/mL and 64% (77/121) of patients with a PSA <0.5 ng/mL had a positive 18F-rhPSMA-7.3 scan by majority read. Regional DR were broadly consistent across all PSA categories. Of note, extrapelvic lesions were observed in 21% (25/121) of patients with a PSA <0.5 ng/mL and 27% (51/188) of all patients with a PSA <1 ng/mL.

CONCLUSION

Among this cohort of patients with low-very low PSA levels, more than two-thirds were found to have positive 18F-rhPSMA-7.3 scans. Of clinical significance, over a quarter of patients had extrapelvic findings. 18F-rhPSMA-7.3 PET may be a useful tool for treatment planning in patients with early biochemical recurrence of prostate cancer where curative salvage therapy is of prime consideration.

Biochemical Relapse-Free Survival in Post-Prostatectomy Patients Receiving 18F-Fluciclovine-Guided Prostate Bed Only Radiation: Post-Hoc Analysis of a Prospective Randomized Trial

PURPOSE/OBJECTIVE(S)

Whole pelvis (WP) radiation therapy (XRT) significantly improved biochemical relapse free survival (bRFS) compared to prostate-bed (PB)-only XRT in RTOG 0534, yet increased toxicity and was performed in an era prior to PET staging (Pollack et al, Lancet, 2022). Separately, 18F-fluciclovine PET/CT (PET)-guided post-prostatectomy XRT demonstrated improved bRFS compared to XRT guided by conventional imaging alone. We hypothesized that patients whose decisions were changed from whole pelvic XRT to PB-only XRT after PET imaging would have bRFS that was (a) not significantly different than patients initially planned for PB-only XRT, and (b) significantly improved over patients planned for WP XRT without PET guidance.

MATERIALS/METHODS

We conducted a post-hoc analysis of a prospective, randomized, single-institution trial comparing conventional (Arm A) v. PET-guided (Arm B) post-prostatectomy XRT. For patients randomized to Arm B, pre-PET treatment field decisions were recorded, and post-fluciclovine fields were rigidly defined per protocol: pN0 patients with no pelvic or extrapelvic PET uptake received PB-only XRT. Three- and four-year bRFS were compared in patients initially planned for WP with change to PB-only XRT [Arm B (WP→PB)] v Arm B patients initially planned for PB-only with final XRT to PB-only [Arm B(PB→PB)] & Arm A patients treated with whole pelvic XRT [Arm A(WP)] using Z test and log-rank test. Demographics were compared using Chi-square test, Fisher's exact test, or ANOVA as appropriate.

RESULTS

We identified 10 Arm B (WP→PB), 31 Arm B (PB→PB), and 25 Arm A (WP) patients. Androgen deprivation was used in 50.0% of Arm B (WP→PB) and 3.2% of Arm B (PB→PB) patients, p<0.01. Mean pre-XRT PSA was significantly higher (1.56 v 0.32 ng/mL, respectively, p<0.01) in Arm B (WP→PB) v Arm B (PB→PB) patients, however, there was no significant difference in extracapsular extension (p = 1.00), seminal vesical invasion (p = 1.00), Gleason score ≥8 (p = 0.58) or margin positivity (p = 0.73) between cohorts. Three- and four-year bRFS was 80% in Arm B (WP→PB) & 87.4% in Arm B (PB→PB), p = 0.47, respectively. Arm A (WP) patients had significantly worse three- (35.2%) and four-year (13.2%) bRFS compared to Arm B (WP→PB), p<0.01.

CONCLUSION

Patients initially planned for WP XRT whose treatment field decisions were changed to PB-only XRT after PET guidance had, in this post-hoc analysis, (a) relapse rates not significantly different than patients initially planned for PB-only XRT and (b) improved relapse rates over patients treated with WP XRT without PET guidance. PET-guided volume de-escalation in selected patients may be one approach to mitigating excess toxicity seen with WP XRT without compromising outcomes and warrants further exploration.

Rapid Unpaired CBCT-Based Synthetic CT for CBCT-Guided Adaptive Radiotherapy

PURPOSE/OBJECTIVE(S)

Quantitative cone beam CT (CBCT) is the foundation for image-guided radiation therapy, improving treatment setup, tumor delineation and dose calculation. However, CBCT images suffer from severe artifacts, limiting clinical utility. Deep learning can overcome these limitations, boosting radiographic and dosimetric quality critical for online adaptive radiotherapy (ART). We hypothesize adapted contrastive unpaired translation (CUT), a recent method for image-to-image translation of photographic images, can improve CBCT quality while reducing compute time, demonstrating utility for ART.

MATERIALS/METHODS

Same-day CBCT and quality assurance CT (QACT) images acquired from 79 patients receiving proton therapy for prostate cancer between 2019 and 2020 at a single institution were retrospectively collected. QACT images were acquired for quality assurance in accordance with institutional policy. Seventy-nine patients yielded 102 non-contrast CBCT-QACT image sets. Each QACT image was rigidly registered to the corresponding CBCT and resampled to 1 × 1 × 2 mm to establish uniform voxel size and spacing. CBCT images were randomly shuffled prior to input to the CUT model for unsupervised training and QACT-quality synthetic CT images were generated as outputs. We compared mean absolute error (MAE), structural similarity index measure (SSIM), and Fréchet inception distance (FID) against same-day QACT.

RESULTS

MAE, SSIM, and FID were compared for the CycleGAN and CUT data relative to input QACT and are reported as the mean across five-fold cross-validation ± standard error. CUT achieved superior performance in MAE (19.5 ± 3.9 HU vs. cycleGAN 47.1 ± 25.4) and FID (31.5 ± 6.6 vs cycleGAN 75.9 ± 41.3). MAE indicates pixel-level correspondence to QACT HU intensity values, making the synthetic outputs of CUT useful for dose calculations during ART. FID further demonstrates perceptual visual similarity. SSIM for CycleGAN (0.7 ± 0.2) and CUT (0.8 ± 0.0) were similar, indicating acceptable reproducibility of global structure. CUT was faster and lighter than CycleGAN. CycleGAN contained a total of 28,286,000 parameters; CUT contained 14,703,000, approximately half that of CycleGAN. As a result, CycleGAN computes on a single CT image slice over 0.33s while CUT requires just 0.18s.

CONCLUSION

The contrastive method investigated here was demonstrated to be faster and more accurate than CycleGAN, requiring fewer networks and parameters to achieve superior performance. We demonstrated anatomic boundary preservation and HU fidelity superior to cycleGAN while significantly reducing compute time. We plan to investigate the use of these synthetic CT images in automated segmentation prior to exploration of CUT in a prospective setting.

Association of Radiation Facility Volume with Overall Survival in Patients with Very High-Risk Prostate Cancer Treated with Radiation and Androgen Deprivation Therapy

PURPOSE/OBJECTIVE(S)

Studies suggest an association of treatment at high volume facilities with improved survival in cancer patients receiving surgery or radiation therapy. This association has not been studied in patients with very high-risk prostate cancer, who are treated using a multimodality approach that often requires specialized care with advanced diagnostic imaging, complex radiotherapeutic planning, and multidrug antiandrogen regimens. We used the National Cancer Database (NCDB) to study the association of radiation treatment facility volume (FV) with overall survival (OS).

MATERIALS/METHODS

We selected for patients with very high risk, localized prostate cancer by NCCN criteria (cT3b-T4, primary Gleason pattern 5, >4 cores with grade group 4-5, and/or 2-3 high risk features). We included patients who received hormone therapy with either external beam radiation to a dose of ≥60 Gy or external beam radiation to a dose of ≥45 Gy combined with brachytherapy. Association of FV with OS was evaluated through a bias-adjusted log-rank test to identify the optimal cut point of FV for dichotomization. Kaplan-Meier curves were used to study the association of binary FV with overall survival (OS) with and without IPTW (inverse probability treatment weighting) balancing the following confounders: age, race, median income, education, insurance, academic treatment facility, Charlson comorbidity score, T stage, PSA, Gleason score, total radiation dose, year of diagnosis, and patient distance from treatment facility. Cox proportional hazards model was built using backward variable selection strategy (α of 0.05 for removal).

RESULTS

We identified 25,219 very high-risk prostate cancer patients by NCCN criteria (median follow up 57.36 months; 95% CI 56.67 - 58.09) diagnosed between 2004 and 2015. High FV (n = 6,438) was associated with better OS on univariable analysis (hazard ratio [HR] = 0.81; 95% confidence interval [CI] 0.77 - 0.86; p < 0.001) and multivariable analysis (HR = 0.89; 95% CI 0.84 - 0.95; p < 0.001). Other factors associated with improved OS on multivariable analysis included younger age, non-white/black race, higher income, private insurance, academic/research treatment facility, lower comorbidity, lower T-stage, lower PSA, and lower Gleason score. After IPTW adjustment, high FV remained associated with better OS (HR = 0.90; 95% CI 0.85 - 0.95; p < 0.001).

CONCLUSION

Patients with NCCN very high-risk prostate cancer treated at a radiation facility with high case volume had better OS than patients treated at a facility with low volume, after adjustment for confounders. This may suggest that for very high-risk patients, outcomes may be improved by the expertise and optimal multidisciplinary care that typically accompany high facility treatment volume.

Prognostic Significance of Pretreatment Immune Cell Infiltration in Muscle Invasive Bladder Cancer Treated with Definitive Chemoradiation: Analysis of NRG RTOG 0524 and 0712

PURPOSE/OBJECTIVE(S)

Chemoradiation therapy (CRT) is an organ conserving approach in the treatment of locally advanced bladder cancer. Chemoradiation is thought to potentially result in immunogenic stimulation, and bladder cancer is often a tumor with high immune cell infiltration. Thus, we aimed to profile the tumor immune microenvironment of bladder cancer and identify prognostic immune biomarkers for CRT response by profiling tumor samples from NRG/RTOG 0524 and 0712, two prospective trials of CRT in muscle invasive bladder cancer (MIBC).

MATERIALS/METHODS

Pretreatment tissue samples from both trials were profiled using Cofactor Genomics ImmunoPrism, an RNA sequencing assay that uses gene expression profiles to quantify immune cell populations in the tumor microenvironment (TME). Differential gene expression was estimated for different immune cell type proportions across samples. Kaplan-Meier survival analysis and log rank tests were performed to evaluate differences in overall survival (OS) stratified by genes influenced by immune cell proportions or genes associated with immune response signatures.

RESULTS

A total of 70 samples (43 from RTOG 0524 and 27 from RTOG 0712) underwent analysis using the ImmunoPrism assay. Immune cell proportions were as follows: CD8 T cells: median 1.2%, CD4 T cells: median 0.8%, Treg cells: median 9.2%, CD19 B cells: median 5.1%, M2 macrophages: median 0.8%, M1 macrophages: median 0%. Unbiased clustering based on gene expression profiles driven by immune cell proportions demonstrated two groups: cluster 1 with a low percentage of immune cells and shorter OS (median 31 months) and cluster 2 with a high percentage of immune cells and longer OS (median 101 months, p = 0.036). Higher expression of genes associated with T cell infiltration (CD8A and ICOS) was associated with improved OS (104 vs 35 months, p = 0.028, HR = 0.48 (0.25 - 0.94), p = 0.031) as was higher expression of IDO1, which is associated with the interferon gamma pathway (104 vs 35 months, p = 0.042, HR = 0.49 (0.24 - 0.99), p = 0.046).

CONCLUSION

Bladder tumors have a wide range of immune cell infiltration in the TME. Increased immune cell proportions are prognostic for OS following CRT, as well as a higher expression of genes associated with T cell infiltration interferon gamma signaling. These findings have implications for the integration of immunotherapy in the definitive management of MIBC; and can be explored further in the ongoing NRG/SWOG 1806 trial.

Plan Quality Analysis of Automated Treatment Planning Workflow With Commercial Auto-Segmentation Tools and Clinical Knowledge-Based Planning Models for Prostate Cancer

This study evaluated the feasibility of using artificial intelligence (AI) segmentation software for volume-modulated arc therapy (VMAT) prostate planning in conjunction with knowledge-based planning to facilitate a fully automated workflow. Two commercially available AI software programs, Radformation AutoContour (Radformation, New York, NY) and Siemens AI-Rad Companion (Siemens Healthineers, Malvern, PA) were used to auto-segment the rectum, bladder, femoral heads, and bowel bag on 30 retrospective clinical cases (10 intact prostate, 10 prostate bed, and 10 prostate and lymph node). Physician-segmented target volumes were transferred to AI structure sets. In-house RapidPlan models were used to generate plans using the original, physician-segmented structure sets as well as Radformation and Siemens AI-generated structure sets. Thus, there were three plans for each of the 30 cases, totaling 90 plans. Following RapidPlan optimization, planning target volume (PTV) coverage was set to 95%. Then, the plans optimized using AI structures were recalculated on the physician structure set with fixed monitor units. In this way, physician contours were used as the gold standard for identifying any clinically relevant differences in dose distributions. One-way analysis of variation (ANOVA) was used for statistical analysis. No statistically significant differences were observed across the three sets of plans for intact prostate, prostate bed, or prostate and lymph nodes. The results indicate that an automated volumetric modulated arc therapy (VMAT) prostate planning workflow can consistently achieve high plan quality. However, our results also show that small but consistent differences in contouring preferences may lead to subtle differences in planning results. Therefore, the clinical implementation of auto-contouring should be carefully validated.

What is the value of digital health?

The panellist Anant Jani will discuss about: What is the value of digital health? There is much hope and hype surrounding the potentially transformative effect that digital health tools can have in health and care systems but it is very difficult to ascertain the true value that digital health tools currently deliver or could deliver in the future. Compounding this uncertainty is the diverse, large and ever-changing digital health landscape - there are currently over 300,000 health and care apps on the market place in comparison to the less than 2000 drugs health and care systems normally have to deal with. In this session, we highlight how the quadruple value framework, recently endorsed by the EU Commission, can be used to help rationalize the digital health ecosystem by promoting the interventions that have the greatest potential to promote primary, secondary or tertiary prevention while optimising resource utilisation.

Creating a common language: defining individualized, personalized and precision prevention in public health

Background

Because of the limited success of population-based prevention methods and due to developments in genomic screening, public health professionals and health policy makers are increasingly interested in more individualized prevention strategies. However, the terminology applied in this field is still ambiguous and thus has the potential to create misunderstandings.

Methods

A narrative literature review was conducted to identify how individualized, personalized and precision prevention are used in research papers and documents. Based on the findings a set of definitions were created that distinguish between these activities in a meaningful way.

Results

Definitions were found only for precision prevention, not for individualized or personalized prevention. The definitions of individualized, personalized and precision medicine were therefore used to create the definitions for their prevention counterparts. By these definitions, individualized prevention consists of all types of prevention that are individual-based; personalized prevention also consists of at least one form of -omic screening; and precision prevention further includes psychological, behavioral and socioeconomic data for each patient.

Conclusions

By defining these three key terms for different types of individual-based prevention both researchers and health policy makers can differentiate and use them in their proper context.

A Prospective Phase 2 Trial of Transperineal Ultrasound-Guided Brachytherapy for Locally Recurrent Prostate Cancer After External Beam Radiation Therapy (NRG Oncology/RTOG-0526)

PURPOSE

Only retrospective data are available for low-dose-rate (LDR) salvage prostate brachytherapy for local recurrence after external beam radiation therapy (EBRT). The primary objective of this prospective phase 2 trial (NCT00450411) was to evaluate late gastrointestinal and genitourinary adverse events (AEs) after salvage LDR brachytherapy.

METHODS AND MATERIALS

Eligible patients had low- or intermediate-risk prostate cancer before EBRT and biopsy-proven recurrence >30 months after EBRT, with prostate-specific antigen levels <10 ng/mL and no regional/distant disease. The primary endpoint was grade 3 or higher late treatment-related gastrointestinal or genitourinary AEs occurring 9 to 24 months after brachytherapy. These AEs were projected to be ≤10%, with ≥20% considered unacceptable. All events were graded with National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Multivariate analyses investigated associations of pretreatment or treatment variables with AEs.

RESULTS

One hundred patients from 20 centers were registered from May 2007 to January 2014. The 92 analyzable patients had a median follow-up of 54 months (range, 4-97) and a median age of 70 years (interquartile range [IQR], 65-74). The initial Gleason score was 7 in 48% of patients. The median dose of EBRT was 74 Gy (IQR, 70-76) at a median interval of 85 months previously (IQR, 60-119). Only 16% had androgen deprivation at study entry. Twelve patients (14%) had late grade 3 gastrointestinal/genitourinary AEs, with no treatment-related grade 4 or 5 AEs. No pretreatment variable predicted late AEs, including prior EBRT dose and elapsed interval. Higher V100 (percentage of prostate enclosed by prescription isodose) predicted both occurrence of late AEs (odds ratio, 1.24; 95% confidence interval, 1.02-1.52; P = .03) and earlier time to first occurrence (hazard ratio, 1.18; 95% CI, 1.03-1.34; P = .02).

CONCLUSIONS

This prospective multicenter trial reports outcomes of salvage LDR brachytherapy for post-EBRT recurrence. The rate of late grade 3 AEs did not exceed the unacceptable threshold. The only factor predictive of late AEs was implant dosimetry reflected by V100. Efficacy outcomes will be reported at a minimum of 5-year follow-up.

Development and Validation of Consensus Contouring Guidelines for Adjuvant Radiation Therapy for Bladder Cancer After Radical Cystectomy

PURPOSE

To develop multi-institutional consensus clinical target volumes (CTVs) and organs at risk (OARs) for male and female bladder cancer patients undergoing adjuvant radiation therapy (RT) in clinical trials.

METHODS AND MATERIALS

We convened a multidisciplinary group of bladder cancer specialists from 15 centers and 5 countries. Six radiation oncologists and 7 urologists participated in the development of the initial contours. The group proposed initial language for the CTVs and OARs, and each radiation oncologist contoured them on computed tomography scans of a male and female cystectomy patient with input from ≥1 urologist. On the basis of the initial contouring, the group updated its CTV and OAR descriptions. The cystectomy bed, the area of greatest controversy, was contoured by another 6 radiation oncologists, and the cystectomy bed contouring language was again updated. To determine whether the revised language produced consistent contours, CTVs and OARs were redrawn by 6 additional radiation oncologists. We evaluated their contours for level of agreement using the Landis-Koch interpretation of the κ statistic.

RESULTS

The group proposed that patients at elevated risk for local-regional failure with negative margins should be treated to the pelvic nodes alone (internal/external iliac, distal common iliac, obturator, and presacral), whereas patients with positive margins should be treated to the pelvic nodes and cystectomy bed. Proposed OARs included the rectum, bowel space, bone marrow, and urinary diversion. Consensus language describing the CTVs and OARs was developed and externally validated. The revised instructions were found to produce consistent contours.

CONCLUSIONS

Consensus descriptions of CTVs and OARs were successfully developed and can be used in clinical trials of adjuvant radiation therapy for bladder cancer.