Patient-Reported Outcomes in Patients With Advanced Urothelial Cancer Who Are Ineligible for Cisplatin and Treated With First-Line Enfortumab Vedotin Alone or With Pembrolizumab

PURPOSE

Locally advanced/metastatic urothelial cancer (la/mUC) affects patients' quality of life (QOL) and functioning. We describe the impact of first-line (1L) enfortumab vedotin (EV) alone or with pembrolizumab (P) on QOL/functioning/symptoms in patients with la/mUC who were cisplatin-ineligible from EV-103 Cohort K.

METHODS

In this phase Ib/II trial, patients were randomly assigned 1:1 to EV + P or EV monotherapy (mono). Exploratory patient-reported outcomes (PROs) were assessed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core Questionnaire (EORTC QLQ-C30) and Brief Pain Inventory Short Form (BPI-SF) at baseline, once per week for cycles 1-3, and then in every cycle through the end of treatment. Changes in scores from baseline to week 24, reported as least squares mean (standard error), were assessed by mixed models for repeated measures. There were no formal statistical comparisons between treatment arms.

RESULTS

Of 149 patients treated, 65 (EV + P) and 63 (EV mono) comprised the PRO analysis set. For EV + P, EORTC QLQ-C30 QOL was maintained through week 24 with improvements in emotional functioning, pain, and insomnia. Clinically meaningful improvements were seen in EORTC QLQ-C30 pain after EV + P at weeks 12 (-14.41 [3.14]) and 24 (-14.99 [3.56]) and BPI-SF worst pain at week 24 (-2.07 [0.37]). For EV mono, EORTC QLQ-C30 QOL remained stable with clinically meaningful improvements in EORTC QLQ-C30 pain (-12.55 [4.27]), insomnia (-14.46 [4.69]), and constipation (-10.09 [4.35]) at week 24. There were small-to-moderate improvements in BPI-SF worst pain at week 24.

CONCLUSION

EV + P in patients with la/mUC who were cisplatin-ineligible was associated with preservation or improvement of QOL/functioning/symptoms. Improvement in pain was seen in both PRO instruments and treatment arms. These data complement clinical outcomes of 1L EV + P.

Immune Modulation with RANKL Blockade through Denosumab Treatment in Patients with Cancer

Denosumab is a fully human mAb that binds receptor activator of NFκB ligand (RANKL). It is routinely administered to patients with cancer to reduce the incidence of new bone metastasis. RANK-RANKL interactions regulate bone turnover by controlling osteoclast recruitment, development, and activity. However, these interactions also can regulate immune cells including dendritic cells and medullary thymic epithelial cells. Inhibition of the latter results in reduced thymic negative selection of T cells and could enhance the generation of tumor-specific T cells. We examined whether administering denosumab could modify modulate circulating immune cells in patients with cancer. Blood was collected from 23 patients with prostate cancer and 3 patients with renal cell carcinoma, all of whom had advanced disease and were receiving denosumab, prior to and during denosumab treatment. Using high-dimensional mass cytometry, we found that denosumab treatment by itself induced modest effects on circulating immune cell frequency and activation. We also found minimal changes in the circulating T-cell repertoire and the frequency of new thymic emigrants with denosumab treatment. However, when we stratified patients by whether they were receiving chemotherapy and/or steroids, patients receiving these concomitant treatments showed significantly greater immune modulation, including an increase in the frequency of natural killer cells early and classical monocytes later. We also saw broad induction of CTLA-4 and TIM3 expression in circulating lymphocytes and some monocyte populations. These findings suggest that denosumab treatment by itself has modest immunomodulatory effects, but when combined with conventional cancer treatments, can lead to the induction of immunologic checkpoints. See related Spotlight by Nasrollahi and Davar, p. 383.

A plain language summary exploring a new treatment combination for untreated locally advanced or metastatic urothelial cancer: enfortumab vedotin plus pembrolizumab

WHAT IS THIS SUMMARY ABOUT?

This summary provides the results of a study of two treatments for cancer, enfortumab vedotin and pembrolizumab, that were studied together against locally advanced or metastatic urothelial cancer (la/mUC), a cancer that occurs most commonly in the bladder.

WHAT WERE THE RESULTS?

In the 45 patients studied, around 16% did have serious side effects, but most side effects were manageable. Twenty-four percent of patients, however, stopped the study treatment because of their side effects. Within about 2 months of starting treatment, most patients' (73%) tumors were smaller and stayed smaller, on average, for more than 2 years.

WHAT DO THE RESULTS MEAN?

The combination of enfortumab vedotin plus pembrolizumab is a new treatment option for patients with locally advanced or metastatic urothelial cancer when they cannot receive the typical treatment, cisplatin. Advanced or metastatic urothelial cancer is a type of cancer where the cancer has already spread outside of the bladder or urinary tract.

Enfortumab Vedotin With or Without Pembrolizumab in Cisplatin-Ineligible Patients With Previously Untreated Locally Advanced or Metastatic Urothelial Cancer

PURPOSE

Patients with locally advanced or metastatic urothelial cancer (la/mUC) who are ineligible for cisplatin-based therapy have limited first-line (1L) treatment options and significant need for improved therapies. Enfortumab vedotin (EV) and pembrolizumab (Pembro) individually have shown a survival benefit in urothelial cancer in second-line + la/mUC settings. Here, we present data from the pivotal trial of EV plus Pembro (EV + Pembro) in the 1L setting.

PATIENTS AND METHODS

In Cohort K of the EV-103 phase Ib/II study, cisplatin-ineligible patients with previously untreated la/mUC were randomly assigned 1:1 to receive EV as monotherapy or in combination with Pembro. The primary end point was confirmed objective response rate (cORR) per blinded independent central review. Secondary end points included duration of response (DOR) and safety. There were no formal statistical comparisons between treatment arms.

RESULTS

The cORR was 64.5% (95% CI, 52.7 to 75.1) and 45.2% (95% CI, 33.5 to 57.3) for patients treated with EV + Pembro (N = 76) and EV monotherapy (N = 73), respectively. The median DOR was not reached for the combination and was 13.2 months for monotherapy; 65.4% and 56.3% of patients who responded to the combination and monotherapy, respectively, maintained a response at 12 months. The most common grade 3 or higher treatment-related adverse events (TRAEs) in patients treated with the combination were maculopapular rash (17.1%), fatigue (9.2%), and neutropenia (9.2%). EV TRAEs of special interest (any grade) in the combination arm included skin reactions (67.1%) and peripheral neuropathy (60.5%).

CONCLUSION

EV + Pembro showed a high cORR with durable responses as 1L treatment in cisplatin-ineligible patients with la/mUC. Patients who received EV monotherapy had a response and safety profile consistent with previous studies. Adverse events for EV + Pembro were manageable, with no new safety signals observed.

Serial stereotactic body radiation therapy for oligometastatic prostate cancer detected by novel PET-based radiotracers

BACKGROUND

Radiopharmaceuticals, including Ga-68-prostate specific membrane antigen (PSMA)-11 and F-18-Fluciclovine, are increasingly used to inform therapies for prostate cancer (CaP). Stereotactic body radiation therapy (SBRT) to PET-detected oligometastatic CaP has been shown to improve progression free survival (PFS) and delay androgen deprivation therapy (ADT) compared to observation. For men who subsequently develop oligorecurrent CaP, outcomes following second SBRT are unknown.

METHODS

A retrospective cohort study was conducted. Eligibility criteria included patients with oligometastatic (1-5 lesions) CaP detected on PSMA or Fluciclovine PET who underwent 2 consecutive SBRT courses to tracer-avid sites. Data on stage, tracer type, concurrent systemic therapy, and prostate-specific antigen (PSA) responses for first SBRT (SBRT1) and second SBRT (SBRT2) were collected. Outcomes included PSA decline ≥50% (PSA50), PFS after SBRT2, and ADT initiation or intensification-free survival after SBRT2. Factors potentially associated with PSA50 after SBRT2 was evaluated with multivariable logistic regression. Factors potentially associated with PFS and ADT initiation/intensification-free survival after SBRT2 were evaluated with separate multivariable Cox proportional-hazards models.

RESULTS

Twenty-five patients were identified. At SBRT2, oligorecurrence was detected on PSMA and Fluciclovine PET in 17 (68%) and 8 (32%) patients, respectively. Fifteen (60%) patients had castration-sensitive disease and 10 (40%) had castration-resistant disease. After SBRT2, 16 (64%) achieved a PSA50 response, median PFS was 11.0mo, and median ADT initiation/intensification-free survival was 23.2mo. On multivariable analysis, maximum percent change in PSA after SBRT1 (OR 0.94, 95%CI 0.88-0.99, P = 0.046) and concurrent change in systemic therapy (OR 21.61, 95%CI 1.12-417.9, P = 0.042) were associated with PSA50 responses after SBRT2. PSA50 response after SBRT1 was associated with improved PFS (HR 0.36, 95%CI 0.00-0.42, P = 0.008) and ADT initiation/intensification-free survival (HR 0.07, 95%CI 0.01-0.68, P = 0.021) after SBRT2. From SBRT1 to last follow-up (median 48 months), 7 (28%) patients remained ADT-free.

CONCLUSIONS

Serial SBRT for oligometastatic CaP detected on PSMA or Fluciclovine PET is feasible and can achieve PSA declines, with or without systemic therapy. Degree of biochemical response to first SBRT warrants further study as a potential predictor of PSA response, PFS, and ADT initiation/intensification-free survival following a subsequent SBRT course. This preliminary evidence provides rationale for larger, prospective studies of this strategy.

Association of biomarkers and outcomes in patients (pts) with metastatic urothelial carcinoma (mUC) treated with immune checkpoint inhibitors (ICIs)

532

Background: ICIs form the backbone of treatment for mUC. However, only a minority of pts benefit and additional biomarkers of ICI response are needed. Methods: In our institution, we identified mUC pts treated with ICI monotherapy who had next generation sequencing (NGS). Somatic alterations present in ≥10% of pts ( ARID1A, CCND1, CDKN2A, CDKN2B, ERBB2, FGF3, FGF4, FGF19, FGFR3, KDM6A, MDM2, MLL2, PIK3CA, RB1, TERTp, TP53, TSC1), as well as DNA-damage response (DDR) alterations and tumor mutational burden (TMB) were analyzed as biomarkers. These biomarkers were individually evaluated in separate multivariate models while accounting for clinical factors including age, BMI, ECOG PS, primary tumor location, histology, hemoglobin, neutrophil to lymphocyte ratio and albumin. Multivariate cox regression and logistic regression models were used to measure hazard ratios (HR) and odds ratios (OR) for overall survival (OS), progression-free survival (PFS) and observed response rate (ORR). Results: Among 152 mUC ICI-treated pts, 107 had NGS data (FoundationOne, UCSF500, Strata), including 85 with TMB data. For the 107 pts with NGS, median age was 70 yrs, majority were male (69, 64%), Caucasian (70, 65%), had pure urothelial histology (57, 53%), and had first-line ICI (55, 51%). ORR was 35%, median PFS was 3.9 mos (95% CI: 2.6-7.5 mos), and median OS was 17.4 mos (95% CI: 14.1-30.6 mos). Biomarkers associated with improved outcomes to ICI, independent of relevant clinical factors, included alterations in ARID1A and DDR, as well as high TMB (>10 Mut/Mb). Inferior outcomes were seen in pts with CDKN2B, KDM6A, FGF3, FGF4, and FGF19 alterations (Table). Conclusions: In this large retrospective multivariate analysis controlling for clinical factors in ICI-treated mUC pts, we found multiple biomarkers associated with improved or inferior outcomes. These hypothesis-generating findings can inform clinical decision making and trial design for mUC pts treated with ICIs, and should be validated in larger cohorts. [Table: see text]

Enfortumab vedotin (EV) alone or in combination with pembrolizumab (P) in previously untreated cisplatin-ineligible patients with locally advanced or metastatic urothelial cancer (la/mUC): Subgroup analyses of confirmed objective response rate (cORR) from EV-103 cohort K

499

Background: In EV-103 Cohort K (NCT03288545), EV and P in combination (EV+P) showed encouraging antitumor activity and a manageable safety profile when used as 1L therapy in patients (pts) w/ la/mUC who are ineligible for cisplatin, a population w/ high unmet need. Here we report results of an analysis of prespecified Cohort K subgroups known to be associated w/ poor outcomes. Methods: Pts who are cisplatin-ineligible w/ previously untreated la/mUC were randomized 1:1 to EV (1.25 mg/kg) as monotherapy on Days 1 and 8 or in combination w/ P (200 mg) on Day 1 of 3-week cycles. Primary endpoint is cORR per RECIST v1.1 by blinded independent central review w/ no formal statistical comparison between arms. Secondary endpoints included duration of response and safety (e.g. treatment-related adverse events, TRAEs). The cORR analysis was performed in prespecified subgroups including age, ECOG PS, liver metastasis, PD-L1 expression status, metastatic disease site at baseline, and primary disease site of origin. Results: 149 pts were treated: EV+P n=76; EV n=73; cORRs across key subgroups for both EV+P and EV monotherapy are shown in the table. For EV+P overall cohort, cORR (95%CI): 64.5% (52.7, 75.1); median DOR was not reached. cORRs were consistent across subgroups for EV+P including those w/ ECOG PS score of 1-2: 62.8% (46.7, 77.0) and presence of liver metastasis: 53.8% (25.1, 80.8). Among TRAEs of special interest in the EV+P arm, skin reactions occurred in n=51 (67.1%); peripheral neuropathy occurred in n=46 (60.5%). For EV+P, 68.4% of pts had TRAEs leading to interruption of either EV or P; 48.7% of pts had TRAEs leading to EV dose reduction. Median duration of EV+P treatment was 11 cycles. Conclusions: EV+P showed promising cORR in 1L cisplatin-ineligible pts w/ la/mUC; activity was consistently observed across a range of pre-specified subgroups including those with poor prognosis. EV+P TRAEs were manageable w/ close monitoring and appropriate dose modifications w/ a meaningful duration of treatment. EV+P has the potential to address high unmet needs in 1L la/mUC and MIBC and is being further evaluated in 3 Phase 3 trials (NCT04223856, NCT04700124, NCT03924895). Clinical trial information: NCT03288545 . [Table: see text]

Association of biomarkers and response to immune checkpoint inhibitors (ICIs) in patients with metastatic urothelial carcinoma (mUC) with high and low tumor mutation burden (TMB)

534

Background: ICIs are frequently used as therapy in mUC, but only a minority of patients (pts) respond to treatment. High TMB is associated with improved outcomes to ICIs. However, much is unknown about biomarkers associated with ICI outcomes in pts with high and low TMB respectively. Methods: We retrospectively identified mUC pts with known TMB status and available next generation sequencing (NGS) results treated with ICI monotherapy at our institution. TMB high was defined as ≥ 10 mutations/Mb, with the rest being TMB low. Somatic alterations present in ≥10% pts ( ARID1A, CCND1, CDKN2A, CDKN2B, ERBB2, FGF3, FGF4, FGF19, FGFR3, KDM6A, MDM2, MLL2, PIK3CA, RB1, TERTp, TP53, TSC1), and presence of DNA damage response (DDR) alterations were assessed as biomarkers of interest. Within the TMB-high and TMB-low pt groups we separately assessed patients based on the presence or absence of these somatic alterations, APOBEC mutational signature and high PD-L1 expression. Log rank test was used to determine differences in overall survival (OS) and progression free survival (PFS) among these groups. P-value ≤0.05 was considered significant. Results: Among 107 mUC pts treated with ICI monotherapy between 12/2014 and 3/2022 who had NGS data (UCSF500, FoundationOne, Strata), 85 pts had TMB data, including 47 TMB high pts and 38 TMB low pts. Among 85 pts with known TMB status, median age was 76 yrs, the majority were male (55, 65%), Caucasian (57, 67%), had pure urothelial histology (46, 55%) and were treated with ICIs in frontline setting (47, 55%). Median OS was 17.2 mos and median PFS was 3.42 mos. In TMB high pts, presence of DDR , MLL2, KDM6A, PIK3CA and TERTp alterations were each associated with improved outcomes, while presence of CDKN2B alterations was associated with inferior outcomes (Table). Among TMB low pts, those with RB1 alterations had shorter mOS (11.3 months vs 17.2 months; p=0.04) compared to wild-type pts. Conclusions: In this single-center retrospective analysis of mUC pts, we identified somatic alterations that were predictive of outcomes with ICI treatment in TMB high and TMB low pts respectively. Further exploration of biomarkers in patients stratified by TMB status is warranted in larger cohorts. [Table: see text]

Patient-reported outcomes (PROs) in cisplatin-ineligible patients (pts) with locally advanced or metastatic urothelial cancer (la/mUC) treated with enfortumab vedotin (EV) alone or in combination with pembrolizumab (P) in the phase 1b/2 EV-103 Cohort K study

439

Background: The EV-103 Cohort K trial evaluated 1L EV+P or EV alone (NCT03288545) in pts with la/mUC who were cisplatin-ineligible. EV+P showed a clinically meaningful objective response rate (64.5%; 95% CI, 52.7–75.1) with a manageable safety profile. Because la/mUC is associated with symptoms with a frequent impact on quality of life (QOL) and functioning (Mamtani et al. JCO 2021), we describe the impact of EV+P or EV alone on QOL and symptoms. Methods: In this open-label, Phase 1b/2 trial, cisplatin-ineligible pts with la/mUC were randomized 1:1 to EV+P or EV alone. For exploratory PRO endpoints, pts completed EORTC QLQ-C30 and the BPI-SF at baseline, weekly for cycles 1–3, and once every cycle for the remainder of treatment period. The PRO analysis set included only pts who were treated and completed the questionnaire at baseline. Mixed effect models for repeated measures (MMRM; least squares [LS] mean, standard error [SE]) not adjusted for multiplicity, estimated change vs baseline until Week 24; established thresholds (EORTC QLQ-C30: 10-point change; BPI-SF: 2-point change) were applied to determine clinically meaningful change. Results: Of the 76 pts treated with EV+P, 65 were included in the PRO analysis set. EORTC QLQ-C30 and BPI-SF were completed by 100% and 95%, respectively, at baseline; compliance rates were ≥84% for both instruments through Week 24. In the EORTC QLQ-C30 MMRM analyses, QOL was maintained through Week 24 for EV+P; functioning and symptom scores remained stable over time, with improvements in emotional functioning, pain and sleep disturbance vs observed baseline. In the EV+P arm, clinically meaningful reductions in pain were seen at Week 12 (-12.64 [3.208]) vs baseline and persisted through Week 24 (-13.20 [3.406]). In the BPI-SF MMRM analyses, worst and average pain, pain interference and severity consistently showed improved scores from Week 4–24 for EV+P; clinically meaningful change in worst pain was seen at Week 21 (-2.08 [0.361]). Similar completion and compliance rates were seen for the EV alone PRO analysis set (n=63). EV alone demonstrated clinically meaningful improvements in pain at Week 24 in the EORTC QLQ-C30 (-10.63 [4.110]) and consistent small-to-moderate improvements in the BPI worst and average pain, and pain severity (0.5–1.0 points). Sleep disturbances demonstrated improvement, and other symptom scales, QOL and functional domains remained stable. Conclusions: PRO data showed that EV+P in cisplatin-ineligible pts with la/mUC was associated with preservation or improvement of QOL, functioning, and symptoms. Improvement in pain was demonstrated consistently in both PRO instruments and treatment arms. These PRO data complement the clinical outcomes of EV+P in 1L cisplatin-ineligible pts with la/mUC. Clinical trial information: NCT03288545 .

Enfortumab Vedotin Plus Pembrolizumab in Previously Untreated Advanced Urothelial Cancer

PURPOSE

Cisplatin-based combination chemotherapy remains the standard of care for locally advanced or metastatic urothelial cancer (la/mUC); however, toxicity is substantial, responses are rarely durable, and many patients with la/mUC are ineligible. Each enfortumab vedotin and pembrolizumab have shown a survival benefit versus chemotherapy in UC, are not restricted by cisplatin eligibility, and warrant investigation as a first-line (1L) combination therapy in patients ineligible for cisplatin.

METHODS

In this ongoing phase Ib/II, multicenter, open-label study, 1L cisplatin-ineligible patients with la/mUC received enfortumab vedotin 1.25 mg/kg once daily on days 1 and 8 and pembrolizumab 200 mg (day 1) intravenously once daily in 3-week cycles. The primary end point was safety. Key secondary end points included confirmed objective response rate, duration of response (DOR), and overall survival (OS).

RESULTS

Forty-five patients received enfortumab vedotin plus pembrolizumab. The most common treatment-related adverse events (TRAEs) were peripheral sensory neuropathy (55.6%), fatigue (51.1%), and alopecia (48.9%). Twenty-nine patients (64.4%) had grade 3 or higher TRAEs; the most common were increased lipase (17.8%), maculopapular rash (11.1%), and fatigue (11.1%). One death (2.2%) was classified as a TRAE. The confirmed objective response rate after a median of nine cycles was 73.3% with a complete response rate of 15.6%. The median DOR and median OS were 25.6 months and 26.1 months, respectively.

CONCLUSION

Enfortumab vedotin plus pembrolizumab showed a manageable safety profile. Most patients experienced tumor shrinkage. The median DOR and median OS exceeding 2 years in a cisplatin-ineligible patient population make this a promising combination currently under investigation in a phase III study (ClinicalTrials.gov identifier: NCT04223856).

TROP2 Expression Across Molecular Subtypes of Urothelial Carcinoma and Enfortumab Vedotin-resistant Cells

Sacituzumab govitecan (SG) is an antibody-drug conjugate (ADC) targeting TROP2, which has recently been approved for treatment-refractory metastatic urothelial cancer (UC). However, the variability of TROP2 expression across different bladder cancer (BC) subtypes, as well as after enfortumab vedotin (EV) exposure, remains unknown. Using gene expression data from four clinical cohorts with >1400 patient samples of muscle-invasive BC and a BC tissue microarray, we found that TROP2 mRNA and protein are highly expressed across basal, luminal, and stroma-rich subtypes, but depleted in the neuroendocrine subtype. In addition, TROP2 mRNA levels are correlated with NECTIN4 mRNA but are more highly expressed than NECTIN4 mRNA in patient cohorts and BC cell lines. Moreover, CRISPR/Cas9-mediated knockdown of TROP2 demonstrates that its expression is one factor governing SG sensitivity. After prolonged EV exposure, cells can downregulate NECTIN4, leading to EV resistance, but retain TROP2 expression and remain sensitive to SG, suggesting nonoverlapping resistance mechanisms to these ADCs. While our findings warrant further validation, they have significant implications for biomarker development, patient selection, and treatment sequencing in the clinic as well as clinical trial design and stratification for metastatic BC patients. PATIENT SUMMARY: In this report, we investigated the expression levels of the drug target TROP2 across different molecular subtypes of bladder cancer in multiple patient cohorts and cell lines. We found high levels of TROP2 in most subtypes except in the neuroendocrine subtype. Overall, TROP2 gene expression is higher than NECTIN4 gene expression, and cells resistant to enfortumab vedotin (EV), a NECTIN4-targeting antibody-drug conjugate, remain sensitive to sacituzumab govitecan (SG). Our findings suggest that SG may be effective across most bladder cancer subtypes, including the bladder cancers previously treated with EV.

Reliability of real-world data for diagnosis of metastatic prostate cancer

397

Background: Real-world data (RWD) is playing an increasingly important role in cancer research. Surrogate endpoints such as metastasis-free survival play an important role in prostate cancer research, leading to interest in its computational extraction, typically with use of International Classification of Disease (ICD) metastatic codes. While prior studies have suggested that ICD codes are valid for identification of patients (pts) with metastatic prostate cancer (MPC), delays in coding may impact their accuracy. The objective of this informatics-based study is to quantify the time delay between diagnosis of MPC and entry of ICD MPC-related code and its interaction with changing institutional healthcare processes. Methods: A single institutional EHR data warehouse was queried to identify a random sample of 100 pts with MPC diagnosis based on ICD codes (ICD10 C79 or ICD9 198.5) from 2013-2021 who were also seen in the genitourinary medical oncology program (GUMOP). Of note, in 6/2018, the GUMOP adopted EHR-specific MPC visit diagnosis identifiers (Dx ID) to improve MPC coding during clinic independent of ICD codes typically used by RWD researchers. Thus, the study cohort was designed to include pts whose first follow up after being diagnosed with MPC was before (n = 50) or after (n = 50) Dx ID implementation. Date of first MPC ICD code entry at any point in the EHR was compared against true date of MPC, based on physician review of definitive imaging or pathology. Data analysis was performed with Wilcox Signed rank test, bivariate analyses, and multivariable linear regression. Covariates included modality of diagnosis confirmation and timing with Dx ID implementation. Results: One hundred pts with MPC ICD coded in the EHR were included, with 29 pts diagnosed by PSMA PET and 71 by conventional imaging. Median time from true MPC diagnosis to first subsequent clinic follow up was < 1 month (IQR 0-2), while median time from true MPC diagnosis to entry of ICD MPC-related code was longer at 4mo (IQR 0-15). 5 pts had C79 applied for N1 disease and 10 pts for work-up of biochemical recurrence. On multivariable analysis of potential factors affecting time interval to MPC ICD entry, Dx ID implementation (b = -6.5 mo [95% CI -1.8 to -11.2], p = 0.007) and non-PSMA based diagnosis (b = -5.7 mo [95% CI -0.5 to -10.8], p = 0.03) were independently associated with shorter time to ICD coding. In subset analysis of the cohort after Dx ID implementation, use of both ICD and Dx ID to identify pts with MPC reduced the median time from true MPC diagnosis to EHR coding (1mo, IQR 0-6.3) compared to ICD alone (2mo, IQR 0-8) (p = 0.003). Conclusions: Timing of MPC ICD entry is highly variable and may carry biases derived from healthcare processes, including data entry and diagnostic testing. This may be improved with EHR workflow interventions. It is essential to have domain knowledge of clinical coding practices to improve information retrieval and recognize potential limitations and biases.

Implementation of a “genetic testing station” in a safety net hospital to optimize access and increase equity

e18565

Background: Diagnosis of hereditary cancers by genetic testing (GT) has significant implications for treatment decisions for individuals and risk reduction among family members. Recent guidelines have expanded the eligibility criteria for GT. However, significant disparities in GT completion persist based on race, ethnicity, insurance status, and English proficiency. Thus, novel interventions are needed to provide diverse populations equitable access to GT. Methods: From March to October 2021, we conducted a single arm study of a genetic testing station (GTS) intervention in a safety net hospital. The GTS intervention included (1) screening of clinic schedules for eligible patients; (2) video-based GT education in English, Spanish, and Cantonese; (3) consent for GT and collection of a blood or saliva sample by a genetic counseling assistant; (4) telehealth-based post-test counseling with a genetic counselor (GC). Bilingual, culturally concordant staff developed the educational videos and study materials. Patients who met the NCCN criteria for GT were eligible. We compared this group to a historical cohort who initiated GT in the preceding nine months. The historical cohort underwent GT in a traditional model: (1) oncologist-initiated referral, (2) pretest counseling with a GC, (3) GT if appropriate, and (4) post-test counseling to review and discuss results. Our primary outcomes were accessibility and feasibility assessed by tracking the implementation process. Secondary outcomes included completion rates of GT and post-test GC visit, and time from enrollment to GT result disclosure. We evaluated all associations with Chi-square tests for categorical variables and Pearson’s Chi-square test of medians for time to post-test visit. Results: We approached 92 patients for GTS; 3 declined, 89 patients underwent the GTS intervention. Of 155 patients (GTS: n = 89, historical cohort: n = 66), 15% were Black, 28% Asian, 17% White, 31% Hispanic/Latinx, 2% Native Hawaiian/Pacific Islander, and 7% multiethnic/other; 51% spoke English, 27% Spanish, 17% Cantonese, and 5% other. In the GTS cohort, 85 (96%) of participants completed GT and 80 (90%) completed the post-test GC visit, compared to 46 (70%, p < 0.001) and 42 (64%, p < 0.001) respectively in the historical cohort. The median time to result disclosure was 30.5 days (IQR 23.8 - 38.8) for the GTS cohort and 80.5 days (IQR 37.5 - 137.5, p = 0.001) for the historical cohort. Conclusions: Implementation of GTS was feasible and acceptable in a safety net setting. GTS resulted in more patients completing GT and post-test counseling and significantly reduced the time to result disclosure, which has the potential to impact treatment decisions and outcomes. As GT eligibility criteria broaden, innovative interventions, workflows, and tailored educational resources for diverse populations are needed to ensure equitable access to GT.

Biomarkers predictive of response to enfortumab vedotin (EV) treatment in advanced urothelial cancer (aUC)

531

Background: EV is an antibody-drug conjugate which recently received full FDA approval for treatment-refractory aUC. Molecular biomarkers and characteristics of patients (pts) most likely to respond to EV therapy have not been well defined. Methods: We retrospectively identified all aUC pts treated with EV at our institution. Clinicopathologic, treatment and response data were abstracted from pt charts. Pts were considered responders to EV if they had a complete response on initial scans after 2-3 months of treatment, or were treated with EV for ≥ 6 months. Responders and non-responders were compared in terms of their molecular and clinical characteristics using Chi-squared test. Most common somatic alterations present in ≥10 pts ( TERTp, TP53, CDKN2A, CDKN2B) were also used to divide pts with available next-generation sequencing (NGS) results into groups with and without these alterations. Log rank test was used to determine differences in overall survival (OS) and progression free survival (PFS) among these groups. Results: Between 1/2020 and 8/2021 a total of 32 pts received EV and 28 had NGS data available with either FoundationOne (14 pts), UCSF500 (13 pts) or Strata (1). Median age was 69.5 years, 24 (75%) were male, 22 (69%) Caucasian, 22 (69%) had pure urothelial histology and 22 (69%) primary tumor location in the bladder. At EV start, 24 (75%) had visceral metastases (mets), 8 (25%) had liver mets, and 13 (41%) had bone mets. Median follow-up from EV start was 12.5 months (range 0.5-36); 20 (63%) pts received EV monotherapy, and 12 (37%) received EV as part of a combination regimen. Non-responders were more likely to have bone metastases (69% vs 21%, p<0.01), but were otherwise similar in baseline clinical characteristics to responders. TP53 alterations were enriched in responders relative to non-responders, whereas non-responders had more CDKN2B alterations (Table). Similar findings were seen in the subset of pts treated with EV monotherapy. Pts with TP53 alterations had longer OS (NR vs 17.0 months, p=0.06) and PFS (NR vs 6.6 months, p=0.04) relative to wild-type pts. Shorter PFS was seen in pts with CDKN2A (4.4 months vs NR, p=0.05) and CDKN2B (4.3 months vs NR, p=0.02) alterations, but no differences in OS were observed. Conclusions: In this retrospective cohort of aUC pts with available NGS data, presence of TP53 and absence of CDKN2A and CDKN2B alterations were associated with favorable responses and improved clinical outcomes with EV, suggesting they may be biomarkers of response to EV. These preliminary findings should be validated in larger cohorts.[Table: see text]

Serial stereotactic body radiation therapy for oligometastatic prostate cancer (PCa) detected by positron emission tomography (PET) imaging

109

Background: Radiopharmaceuticals, including Ga-68-prostate specific membrane antigen (PSMA)-11, F-18-fluciclovine, and choline C-11, are increasingly used to stage and inform therapies for PCa. Stereotactic body radiation therapy (SBRT) to PET-detected oligometastatic PCa has been shown to improve progression free survival (PFS) compared to observation. However, for men who subsequently develop oligorecurrent disease, outcomes following second SBRT are unknown. Methods: A retrospective, single-center, cohort study was conducted. Pts were identified through electronic health records. Inclusion criteria included pts with oligometastatic (1-5 lesions) PCa detected on PSMA, fluciclovine, or choline C-11 PET who underwent 2 consecutive courses of SBRT to tracer-avid oligometastatic disease between 7/2013 and 7/2021. Exclusion criteria included presence of visceral metastases and pure small cell neuroendocrine PCa. Data on stage, tracer type, concurrent systemic therapy, and prostate-specific antigen (PSA) responses for first SBRT (SBRT1) and second SBRT (SBRT2) were collected. Outcomes included PSA decline of ≥50% (PSA50), ≥90% (PSA90), and PSA-PFS. SBRT2 outcomes were compared based on change of concurrent systemic therapy with SBRT2 (e.g., addition of abiraterone or anti-androgen withdrawal) and PSA50 to SBRT1 using Fisher’s exact text and Wilcoxon rank sum test, respectively. Results: A total of 12 pts met eligibility criteria. At SBRT1, 10 (83%) pts had hormone-sensitive PCa (HSPC) and 2 (17%) had castration-resistant PCa (CRPC). For PET tracers, 7 (58%) used PSMA, 4 (33%) fluciclovine, and 1 (8%) choline. After SBRT1, 12 pts (100%) had a PSA decline, 8 (67%) had a PSA50 response, and 6 (50%) a PSA90 response. Median PSA PFS after SBRT1 was 30mo (95%CI 9-65mo). Six (50%) SBRT1 pts had a concurrent change in systemic therapy. At SBRT2, 8 (67%) pts had HSPC and 4 (33%) had CRPC; 7 (58%) used PSMA and 5 (42%) fluciclovine. After SBRT2, 12 (100%) pts had a PSA decline, 8 (67%) had a PSA50 response, and 8 (67%) a PSA90 response. After SBRT2, median PSA PFS was 23mo (95%CI 12-35mo). Among 7 pts who had a concurrent change in systemic therapy with SBRT2, all (100%) had a PSA50 response; among 5 who did not (4 of whom did not receive any systemic therapy), 1 (20%) had a PSA50 response (P=0.01). Among 8 pts who had a PSA50 response to SBRT1, 7 (88%) had one to SBRT2; among 4 who did not have a PSA50 response to SBRT1, 1 (25%) had one to SBRT2 (P=0.01). No complications related to SBRT were documented. Conclusions: Serial SBRT for oligometastatic PCa detected on fluciclovine, PSMA, or choline PET is feasible and can achieve PSA declines independent of systemic therapy. PSA responses were greater when systemic therapy was changed. This preliminary evidence of benefit, based on PSA responses and PSA PFS, provides rationale for larger, prospective studies of serial SBRT for oligometastatic PCa.

Changes in older adults' life space during lung cancer treatment: A mixed methods cohort study

BACKGROUND

Maintenance of function during cancer treatment is important to older adults. Characteristics associated with pretreatment life-space mobility and changes during non-small cell lung cancer (NSCLC) treatment remain unknown.

METHODS

This mixed methods cohort study recruited adults age ≥65 with advanced NSCLC starting palliative chemotherapy, immunotherapy, and/or targeted therapy from a Comprehensive Cancer Center, Veterans Affairs, and safety-net clinic. Patients completed geriatric assessments including Life-Space Assessment (LSA) pretreatment and at 1, 2, 4, and 6 months after treatment initiation. LSA scores range from 0 to 120 (greater mobility); LSA <60 is considered restricted. We used mixed-effects models to examine pretreatment LSA, change from 0 to 1 month, and change from 1 to 6 months. A subgroup participated in semistructured interviews pretreatment and at 2 and 6 months to understand the patient experience of life-space change. For each interview participant, we created joint displays of longitudinal LSA scores juxtaposed with illustrative quotes.

RESULTS

Among 93 patients, median age was 73 (range 65-94). Mean pretreatment LSA score was 67.1. On average, LSA declined 10.1 points from pretreatment to 1 month and remained stable at 6 months. Pretreatment LSA score was associated with several demographic, clinical, geriatric assessment, and symptom characteristics. LSA decline at 1 month was greater among patients with high anxiety (slope = -12.6 vs. -2.3, p = 0.048). Pretreatment body mass index <21 kg/m2 was associated with LSA improvement from 1 to 6 months (slope = 4.1 vs. -0.04, p = 0.003). Joint displays illustrated the impact of different life-space trajectories on patients' lives in their words.

CONCLUSION

Older adults with NSCLC have low pretreatment life space with many developing restricted life space during treatment. Incorporating life-space assessments into clinical cancer care may help older adults concretely visualize how treatment might impact their daily function to allow for informed decision making and identify early changes in mobility to implement supportive interventions.

Efficacy of enfortumab vedotin in advanced urothelial cancer: Analysis from the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) study

BACKGROUND

Enfortumab vedotin (EV) is a novel antibody-drug conjugate approved for advanced urothelial cancer (aUC) refractory to prior therapy. In the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) study, the authors looked at the experience with EV in patient subsets of interest for which activity had not been well defined in clinical trials.

METHODS

UNITE was a retrospective study of patients with aUC treated with recently approved agents. This initial analysis focused on patients treated with EV. Patient data were abstracted from chart reviews by investigators at each site. The observed response rate (ORR) was investigator-assessed for patients with at least 1 post-baseline scan or clear evidence of clinical progression. ORRs were compared across subsets of interest for patients treated with EV monotherapy.

RESULTS

The initial UNITE analysis included 304 patients from 16 institutions; 260 of these patients were treated with EV monotherapy and included in the analyses. In the monotherapy cohort, the ORR was 52%, and it was >40% in all reported subsets of interest, including patients with comorbidities previously excluded from clinical trials (baseline renal impairment, diabetes, and neuropathy) and patients with fibroblast growth factor receptor 3 (FGFR3) alterations. Progression-free survival and overall survival were 6.8 and 14.4 months, respectively. Patients with a pure urothelial histology had a higher ORR than patients with a variant histology component (58% vs 42%; P = .06).

CONCLUSIONS

In a large retrospective cohort, responses to EV monotherapy were consistent with data previously reported in clinical trials and were also observed in various patient subsets, including patients with variant histology, patients with FGFR3 alterations, and patients previously excluded from clinical trials with an estimated glomerular filtration rate < 30 mL/min and significant comorbidities.

LAY SUMMARY

Enfortumab vedotin, approved by the Food and Drug Administration in 2019, is an important new drug for the treatment of patients with advanced bladder cancer. This study looks at the effectiveness of enfortumab vedotin as it has been used at multiple centers since approval, and focuses on important patient populations previously excluded from clinical trials. These populations include patients with decreased kidney function, diabetes, and important mutations. Enfortumab vedotin is effective for treating these patients. Previously reported clinical trial data have been replicated in this real-world setting, and support the use of this drug in broader patient populations.

Heterogeneity in NECTIN4 Expression Across Molecular Subtypes of Urothelial Cancer Mediates Sensitivity to Enfortumab Vedotin

PURPOSE

Enfortumab vedotin (EV) is an antibody-drug conjugate (ADC) targeting NECTIN4 (encoded by the PVRL4/NECTIN4 gene) approved for treatment-refractory metastatic urothelial cancer. Factors that mediate sensitivity or resistance to EV are unknown. In this study, we sought to (i) examine heterogeneity of NECTIN4 gene expression across molecular subtypes of bladder cancer and (ii) determine whether NECTIN4 expression mediates EV sensitivity or resistance.

EXPERIMENTAL DESIGN

Molecular subtyping and NECTIN4 expression data from seven muscle-invasive bladder cancer clinical cohorts (n = 1,915 total specimens) were used to assess NECTIN4 expression across molecular subtypes. The outcome of the transcriptomic analysis was relative NECTIN4 expression in the consensus molecular subtypes of bladder cancer. Expression of NECTIN4 was validated in bladder cancer cell lines. NECTIN4 was stably overexpressed or knocked down in basal and luminal bladder cancer cell lines and EV drug sensitivity assays were performed, as measured by cell proliferation and clonogenic assays.

RESULTS

NECTIN4 expression is heterogenous across molecular subtypes of bladder cancer and significantly enriched in luminal subtypes. NECTIN4 expression is positively correlated with luminal markers GATA3, FOXA1, and PPARG across all cohorts. NECTIN4 expression is both necessary and sufficient for EV sensitivity in luminal and basal subtypes of urothelial bladder cancer cells. Downregulation of NECTIN4 leads to EV resistance.

CONCLUSIONS

Sensitivity to EV is mediated by expression of NECTIN4, which is enriched in luminal subtypes of bladder cancer. These findings may have implications for biomarker development, patient selection, and the inclusion of molecular subtyping in ongoing and future EV clinical trials.See related commentary by Teo and Rosenberg, p. 4950.

A phase (Ph) 1b/2 study of ribociclib (R) in combination with docetaxel (D) plus prednisone (P) in metastatic castration-resistant prostate cancer (mCRPC)

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Background: The survival benefit of D in mCRPC is modest. CDK4/6 inhibitors such as R have shown synergistic activity with taxanes in pre-clinical cancer models. We sought to determine the safety and efficacy of R + D + P in mCRPC patients (pts). Methods: This was a Ph 1b/2 multicenter, open-label single arm trial of mCRPC pts with progression (PD) on ≥ 1 prior androgen receptor signaling inhibitor (ARSi) who had not previously received D for mCRPC (NCT02494921). Pts were treated with escalating doses of R in combination with D + P for 6-9 cycles, followed by single agent maintenance R until radiographic or clinical PD. The Ph 2 primary endpoint was 6-month (mo) radiographic progression-free survival (rPFS) rate by PCWG2 criteria, with a target rate of 55% and null hypothesis of 35%. Ph 2 pts underwent baseline circulating tumor cell (CTC) enumeration and genome sequencing (Epic Sciences). Cox proportional hazard model and log-rank test were used to test for associations between rPFS and CTC burden and copy number (CN) variants, respectively. Results: 43 pts were enrolled from 11/2015 to 6/2019. Median age was 68 (range 55-84). 20.9% of pts had visceral metastases. 33 (77%) had PD on prior abiraterone, 27 (63%) on enzalutamide, and 17 (40%) on both. In Ph 1b, 19 pts were enrolled. In the first cohort (D 75 mg/m2 day [d] 1, R 200 mg/d d2-14 of every 21d cycle), 2 pts experienced DLTs (febrile neutropenia [FN] and grade 4 neutropenia). With an alternative dosing schema of D 60 mg/m2 on d1, and R daily on d1-4 and 8-15 of cycle, with daily G-CSF support on d5-7, the MTD was not reached and D 60 mg/m2 + R 400 mg/d was chosen as the recommended Ph 2 dose (RP2D). In total, 30 pts were treated at RP2D; median number of D cycles was 8.5 and 60% went on to receive maintenance R. The Ph 2 primary endpoint was met with a 6-mo rPFS rate of 65% (95% CI 50-85%). Median rPFS was 8.0 mos (95% CI 4.1-10.0). PSA response rate (RR) defined as ≥50% reduction was 27.6% (95% CI 12.7-47.2%) and objective RR was 30.8% (95% CI 9.1-61.4%). Among pts treated at RP2D, the most common grade ≥3 treatment-related adverse events were neutropenia (n= 11, 36.7%), lymphocytopenia (n=3, 10%); no cases of FN were observed. Baseline CTC burden was associated with an increased risk of radiographic PD or death (HR 1.038, 95% CI 1.001-1.074, p = 0.038). Pts harboring CTCs without MYC (4/11 pts) or CDK6 CN gain (7/11 pts) had prolonged rPFS compared to those with gene amplification (median rPFS 10.76 vs 4.11 mos, p = 0.03, and 7.01 vs 1.92 mos, p = 0.053, respectively). Conclusions: The combination of R + D was well tolerated and showed promising activity in mCRPC pts who had progressed on an ARSi. The Ph 2 study met its primary endpoint, with an encouraging 6-mo rPFS rate of 65%. Lack of MYC or CDK6 amplification on CTC sequencing was associated with longer rPFS. Funding: Novartis Pharmaceuticals, PCF YIA. Managed by the PCCTC. Clinical trial information: NCT02494921.

Updated results of phase II trial using escalating doses of neoadjuvant atezolizumab for cisplatin-ineligible patients with nonmetastatic urothelial cancer (NCT02451423)

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Background: Patients (pts) with muscle-invasive bladder cancer (MIBC) ineligible for cisplatin-based chemotherapy have no standard systemic therapy options and are prioritized for radical cystectomy (RC) alone. This prospective clinical trial investigated the safety and efficacy of escalating doses of neoadjuvant atezolizumab (N-ATZ) prior to RC in MIBC pts. Methods: This is a single-institution, phase II trial of escalating doses of N-ATZ (1200 mg IV every 3 weeks) in pts with MIBC. Key inclusion criteria were resectable urothelial carcinoma of the bladder (T2-T4a,N0-1,M0) and inability to receive cisplatin-based treatment (eGFR < 60 mL/min, G≥2 neuropathy/hearing loss, pt decision). Pts with high-risk disease at RC were eligible to receive adjuvant ATZ for up to 16 total doses. Pts were followed for up to 2 years following RC. Primary efficacy endpoint was pathologic complete response (pCR; pT0N0). Secondary endpoints were safety of treatment, rate of pathologic downstaging (≤pT1N0), response based on PD-L1 status, and overall survival (OS) and recurrence-free survival (RFS) at 1 and 2 years from RC. Results: A total of 20 pts were enrolled and sequentially treated with one (n=6), two (n=5), and three (n=9) cycles of N-ATZ prior to RC. Median age was 69 (range 61-81), 75% were male and 85% Caucasian. Pts were cisplatin-ineligible due to low GFR (35%), hearing loss (25%) or neuropathy (10%); the rest refused cisplatin (30%). Most pts had pT2 disease (80%); the remainder, pT3/pT4 (15%/5%), and 10% had cN1. Among 17 pts with available tumor PD-L1 status, 76% had PD-L1 positive (CPS≥10) tumors. pCR was observed in 2 pts (10%) with 1 and 2 ATZ doses, whereas pathologic downstaging was observed in 5 pts (25%) across all 3 doses (Table). All pts completed intended treatment and RC within the trial-defined timeframe. Perioperative TRAEs of any grade occurred in 75%, but only 10% had G3 TRAEs (diarrhea, fecal incontinence). There were no G4/G5 events. Median follow-up from RC was 23.6 months and 75% were still followed at the time of data cutoff in 2/2021. Among evaluable pts, 1-year RFS and OS were 72% and 94% while 2-year RFS and OS were 64% and 69%. PD-L1 positive pts had superior OS (logrank p=0.06) and RFS (p=0.10) relative to PD-L1 negative pts. Conclusions: N-ATZ was well tolerated at all three dose levels and did not delay or prevent surgery. As few as 1 to 2 ATZ doses resulted in pathologic downstaging, including pCR. Although pCR rate in this trial was lower than expected, most pts had a durable recurrence-free period and all evaluable pts with tumor downstaging were alive and recurrence-free at 2 years following RC. Increased tumor PD-L1 expression was suggestive of improved outcomes and further biomarker analyses are ongoing. Clinical trial information: NCT02451423. [Table: see text]

Immunogenic priming with 177Lu-PSMA-617 plus pembrolizumab in metastatic castration resistant prostate cancer (mCRPC): A phase 1b study

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Background: Immune checkpoint inhibitors have limited single agent activity in microsatellite-stable mCRPC. 177Lu-PSMA-617 (Lu) is a PSMA-targeting radioligand therapy that has demonstrated promising anti-tumor activity. We sought to determine whether a single dose of Lu can induce an immunogenic priming effect to improve outcomes of men with mCRPC subsequently treated with pembrolizumab (P). Methods: We undertook a phase 1b, single arm trial enrolling chemotherapy-naïve mCRPC patients (pts) with progression (PD) on at least one prior androgen signaling inhibitor (NCT03805594). Pts were required to have ≥ 3 PSMA-avid lesions on 68Ga-PSMA-11 PET and measurable disease by RECIST 1.1 criteria. No genomic selection was undertaken. Pts were enrolled sequentially on one of three schedules: A) Single dose of Lu (7.4 GBq) followed by initiation of P (200 mg IV q 3 weeks) 28 days later; B) Lu x 1 dose given concomitantly with first P administration; C) Lu x 1 dose given on C2D1 following initiation of P on C1D1. Pts were treated with P until confirmed radiographic or clinical PD. The primary endpoint was safety; key secondary endpoints included PSA response, objective response rate by RECIST 1.1 criteria (ORR), median duration of response (DOR), and radiographic progression-free survival (rPFS). Results: 18 pts were enrolled, 6 per schedule. The median age was 64 (range 51 – 80) and 44% of pts had visceral metastases. The median baseline number of PSMA-avid metastatic lesions was 20 (range 6 – 50+). Six pts (33%) had progressed on prior abiraterone, 4 (22%) on enzalutamide, and 8 (44%) on both. There were no dose-limiting toxicities and one Grade ≥ 3 treatment-related adverse event (AE) (inflammatory arthritis, schedule B). There were no grade ≥ 3 hematologic AEs. The ORR was 8/18 (44%) and median DOR has not been reached (range 1.9+ – 15.9+ months). Four pts (2 on schedule A, 1 on schedule B, 1 on schedule C) with durable partial responses remain on study treatment for 5.4+, 8.9+, 9.2+, and 17.8+ months, respectively. The median rPFS was 6.5 months (95% CI: 2.5 – 9.8). PSA30, PSA50, and PSA90 response rates were 44%, 28%, and 17%, respectively. Fourteen pts (78%), including all durable responders, had somatic genomic data available. One (7%) harbored a DNA repair mutation ( BRCA1, non-responder), none were MSI-high, and all carried low tumor mutational burden (≤ 5 mutations/MB). Single cell sequencing of the immune microenvironment from paired metastatic tumor biopsies is underway. Conclusions: 177Lu-PSMA-617 as a priming dose followed by pembrolizumab was well tolerated and leads to durable responses in a subset of mCRPC without high mutational burden or microsatellite instability, suggesting a possible immunogenic priming effect of radioligand therapy. Further evaluation of the combination is ongoing in a phase 2 study. Clinical trial information: NCT03805594.

Study EV-103: Update on durability results and long term outcome of enfortumab vedotin + pembrolizumab in first line locally advanced or metastatic urothelial carcinoma (la/mUC)

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Background: Significant unmet need remains for people with cisplatin-ineligible (cis-ineligible) locally advanced or metastatic urothelial carcinoma (la/mUC). In the first-line (1L) setting, carboplatin-based regimens have demonstrated poor tolerability, modest objective response rate (ORR) and limited durability. PD-1/PD-L1 inhibitors demonstrate durable responses; however, only a minority of pts achieve a response (ORR 24-29%). Enfortumab vedotin (EV) is an antibody-drug conjugate (ADC) delivering the microtubule-disrupting agent monomethyl auristatin E (MMAE) to targeted tumor cells expressing Nectin-4. EV has shown an overall survival benefit versus chemotherapy in previously treated la/mUC. Preclinical studies show that ADCs utilizing MMAE can induce immunogenic cell death and may enhance antitumor immunity. Clinical data suggests the combination of EV + pembrolizumab (P) may have the potential to induce greater antitumor activity compared to either agent alone. Preliminary data on EV + P was previously presented, and the FDA granted breakthrough therapy designation to EV + P for the treatment of pts with 1L cis-ineligible la/mUC in Feb 2020. Here we report updated data with 24.9 months median follow-up. Methods: This multi-cohort EV-103 study (NCT03288545) evaluates the safety/activity of EV + P (Dose Escalation/Cohort A). This report highlights 1L cis-ineligible pts treated with 3-week cycles of EV 1.25 mg/kg (Days 1, 8) and P (Day 1). Endpoints include safety/tolerability, investigator response per RECIST v1.1, DOR, PFS, and OS. Results: As of 13 Oct 2020, the median follow-up for the 45 1L la/mUC pts (median age 69 yrs [51-90]) was 24.9 months. The median number cycles of EV + P was 9 (range 1-34). The most common treatment-related adverse events were peripheral sensory neuropathy (56%, 4% ≥G3), fatigue (51%, 11% ≥G3), and alopecia (49%). There was one death reported as possibly related to study treatment (multiple organ dysfunction syndrome) per investigator assessment. Confirmed ORR is 73.3% (95% CI: 58.1, 85.4) including 17.8% CR and an ORR of 57.1% (8/14) in pts with liver metastasis. The median DOR was 25.6 months (95% CI: 8.3, -). Fifty-three percent of the responders had DOR at 24 months. Additionally, the DCR is 93.3%, the median PFS is 12.3 months (95% CI: 8.0, -), and the median OS is not reached. The OS rate at 24 months is 56.3% (95% CI: 39.8, 69.9). Conclusions: EV + P, a platinum-free option, continues to demonstrate promising activity with a durable response profile in 1L cis-ineligible pts with la/mUC. The safety profile is manageable and stable over time with no new safety signals. Cohort K of EV-103 in cis-ineligible pts with la/mUC is actively randomizing pts to EV monotherapy or EV + P to evaluate the contribution of each agent. Clinical trial information: NCT03288545.

Rate of skeletal-related events (SREs) for abiraterone acetate (AA) versus enzalutamide (ENZ) in prostate cancer: A population-based study using the SEER-Medicare database

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Background: Skeletal-related events are common in men with prostate cancer, and are associated with significant morbidity and mortality. AA and ENZ are novel androgen signaling inhibitors used in the treatment of metastatic prostate castration-resistant prostate cancer (mCRPC). As directly comparative efficacy data do not exist between AA and ENZ, the differing toxicity profiles inform treatment selection. It is unknown whether SRE rates differ in a real-world population between AA, which is given with corticosteroids, and ENZ, which is associated with imbalance and falls. Methods: The national SEER-Medicare linked database was used to identify men with prostate cancer who received AA or ENZ between 2011-2015; approval during this period was solely for mCRPC. Inclusion criteria included Medicare Part A+B coverage 1 year before and after first receipt of AA/ENZ, without any HMO enrollment. Baseline demographic and comorbidity data were gathered. Diagnosis and procedure claims codes were used to identify SREs, defined as pathologic fracture, surgery to bone, radiation to bone, or spinal cord compression. The time to SRE was defined as time from first receipt of AA/ENZ to the first SRE of any type. A multivariable competing risk regression analysis including death as a competing risk was performed. Results: 5,856 men with prostate cancer who first received AA (N = 4,207) or ENZ (N = 1,649) were identified. The median age at initiation of AA/ENZ was 70 years (range 65-101); 78% were White, 12% Black, 4% Hispanic, 3% Asian, and 4% Other. The median follow-up was 14 months. The overall SRE rate was 13.1% after AA/ENZ start: 574 (13.6%) AA and 194 (11.8%) ENZ, with a cumulative incidence of 11.9% at 2 years. Median overall survival was 16 months (14.4 months for AA and 18.3 months for ENZ). Age, stage at diagnosis, race/ethnicity, baseline comorbidities, and prior history of SRE were balanced between AA vs ENZ, aside from baseline osteoarthritis or rheumatoid arthritis (48.0% AA vs 53.2% ENZ, P < 0.001) and baseline Alzheimer’s dementia (9.2% AA vs 11.1% ENZ, P = 0.03). After controlling for these potential risk factors, receipt of AA versus ENZ was not associated with time to SRE (relative risk ratio [RR] = 0.90, 95% CI 0.77-1.06, P = 0.22). Osteoporosis (RR 1.22, 95% CI 1.01-1.49, P = 0.04), osteoarthritis or rheumatoid arthritis (RR 1.23, 95% CI 1.06-1.43, P < 0.01), and prior history of SRE (RR 1.31, 95% CI 1.07-1.59, P < 0.01) were statistically significant risk factors for SRE. Conclusions: In this real-world population of men with prostate cancer, there was no difference in time to SRE between AA and ENZ. Clinical decision-making on whether to prescribe AA or ENZ should be informed by other potential toxicities as well as cross-resistance with sequencing of these therapies. Analysis of impact of bone protective agent use is underway.

The impact of prior radiation therapy on outcome in a phase 2 trial combining sipuleucel-T (SipT) and ipilimumab (Ipi) in patients (pts) with metastatic castration resistant prostate cancer (mCRPC)

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Background: SipT is an FDA-approved autologous cellular immunotherapy targeting Prostatic Acid Phosphatase (PAP) that improves survival in patients with mCRPC. Combining immunotherapies could provide opportunities to enhance efficacy. We performed a randomized phase II trial adding CTLA-4 blockade with Ipi following SipT treatment and assessed whether timing of this sequence could modify immune and/or clinical responses to this treatment. Methods: Fifty chemotherapy-naïve mCRPC pts were randomized to receive ipi (4 doses of 3mg/kg every 3 weeks) either immediately (n = 24) or 3 weeks (n = 26) following completion of sipT. Blood was collected at various time points of the study. Immune-related adverse events (irAE) were recorded. The primary endpoint was to determine the proportion of pts who achieved an antibody titer of ³1:400 to PA2024, the targeting cassette in SipT and/or PAP. Clinical response was defined as ³30% reduction in serum prostate specific antigen (PSA) compared to pre-treatment levels. Radiographic progression-free survival (rPFS) and overall survival (OS) were defined as from the date of randomization to the date of radiographic progression and the date of death, respectively, or last follow-up date. Luminex assays for anti-PAP and anti-PA2024 specific serum IgG and ELISpot for IFN-g production against PAP and PA2024 were used to assess antigen-specific B and T cells responses, respectively. Modulation of circulating immune cells was evaluated by CyTOF. Results: SipT + Ipi did not induce any unexpected irAEs. The timing of Ipi did not significantly alter the rates of clinical response, rPFS, OS, toxicity, nor antigen-specific B and T cell responses. Clinical responses were observed in 6 of 50 (12%) pts and were often durable (median 140 days, range 55-689 days). Pts experiencing irAEs were more likely to have a PSA response (P = 0.001). The median rPFS was 5.7 months (mos). The median OS was 31.9 mos. This treatment induced antibody and T cell immune responses irrespective of treatment arm. Single cell assessment bt CyTOF demonstrated that treatment induced CD4 and CD8 T cell activation that was more pronounced with the immediate schedule. Lower frequencies of CTLA-4 positive circulating T cells were associated with better clinical outcomes even at baseline. Lower frequencies of CTLA-4 positive T cells was associated with prior radiation therapy. Prior radiation treatment was associated with improved rPFS (6.5 vs. 3.9 mos, P = 0.004). Conclusions: These findings suggest that pre-existing immunity may help dictate responsiveness to Ipi and SipT combination immunotherapy in mCRPC pts. Prior radiation therapy seems to leave not only a lasting impression on the T cell compartment, but also can associate with improved clinical outcomes with subsequent immunotherapy. Clinical trial information: NCT01804465.

TERT promoter mutations and other prognostic factors in patients with advanced urothelial carcinoma treated with an immune checkpoint inhibitor

BACKGROUND

Immune checkpoint inhibitors (ICI) can achieve durable responses in a subset of patients with locally advanced or metastatic urothelial carcinoma (aUC). The use of tumor genomic profiling in clinical practice may help suggest biomarkers to identify patients most likely to benefit from ICI.

METHODS

We undertook a retrospective analysis of patients treated with an ICI for aUC at a large academic medical center. Patient clinical and histopathological variables were collected. Responses to treatment were assessed for all patients with at least one post-baseline scan or clear evidence of clinical progression following treatment start. Genomic profiling information was also collected for patients when available. Associations between patient clinical/genomic characteristics and objective response were assessed by logistic regression; associations between the characteristics and progression-free survival (PFS) and overall survival (OS) were examined by Cox regression. Multivariable analyses were performed to identify independent prognostic factors.

RESULTS

We identified 119 aUC patients treated with an ICI from December 2014 to January 2020. Genomic profiling was available for 78 patients. Overall response rate to ICI was 29%, and median OS (mOS) was 13.4 months. Favorable performance status at the start of therapy was associated with improved OS (HR 0.46, p=0.025) after accounting for other covariates. Similarly, the presence of a TERT promoter mutation was an independent predictor of improved PFS (HR 0.38, p=0.012) and OS (HR 0.32, p=0.037) among patients who had genomic profiling available. Patients with both a favorable performance status and a TERT promoter mutation had a particularly good prognosis with mOS of 21.1 months as compared with 7.5 months in all other patients (p=0.03).

CONCLUSIONS

The presence of a TERT promoter mutation was an independent predictor of improved OS in a cohort of aUC patients treated with an ICI who had genomic data available. Most of the clinical and laboratory variables previously shown to be prognostic in aUC patients treated with chemotherapy did not have prognostic value among patients treated with an ICI. Genomic profiling may provide important prognostic information and affect clinical decision making in this patient population. Validation of these findings in prospective patient cohorts is needed.

Phase II trial of escalating doses of neoadjuvant atezolizumab for patients with non-metastatic urothelial carcinoma ineligible for cisplatin-based neoadjuvant chemotherapy

442

Background: For patients (pts) with muscle-invasive bladder cancer (MIBC) who are ineligible for cisplatin-based chemotherapy (cisplatin), the standard of care option is radical cystectomy (RC) alone. This prospective clinical trial investigated the safety and efficacy of escalating doses of atezolizumab (ATZ) as neoadjuvant therapy prior to RC in pts with non-metastatic urothelial cancer. Methods: This single-arm, single institution, phase II trial investigated the administration of one (n = 6), two (n = 5) or three (n = 9) cycles of ATZ (1200 mg IV given every 3 weeks) in pts with MIBC who are either ineligible for or refused cisplatin prior to RC. Key inclusion criteria were urothelial carcinoma of the bladder (T2-T4a,N0-1,M0) and inability to receive cisplatin-based treatment (eGFR < 60 mL/min, G≥2 neuropathy/hearing loss, pt decision). Pts with high-risk disease ( > pT2 or LN+) at the time of RC were eligible to receive adjuvant ATZ for up to 16 total cycles. Primary efficacy endpoint was pathologic complete response (pCR; pT0N0). Important secondary endpoints were safety of treatment, rates of pathologic downstaging and biomarker assessments in serial tissue samples. Pts were followed for up to 2 years following RC. Results: Among 20 pts with MIBC, median age was 69 (range 61-81) and 75% were male. Most commonly pts were cisplatin-ineligible due to low GFR (35%), hearing loss (25%) or neuropathy (10%); remainder refused cisplatin (30%). At trial enrollment, pT2, pT3, and pT4 was present in 80%, 15%, and 5% of pts and 10% had enlarged pelvic lymph nodes ( > 10 mm) on scans. All pts completed intended treatment cycles and all had RC within the defined timeframe ( > 3 weeks from last and < 12 weeks from first treatment). pCR at RC was 10% (2/20 pts), and was observed in pts receiving 1 and 2 cycles of ATZ. Pathologic downstaging (≤pT1N0) was achieved in 25% (5/20 pts) and observed across all three dose levels. Adjuvant ATZ was given to 8 pts. TRAEs of any grade during perioperative period occurred in 75% and G3 TRAEs in 10% (diarrhea, fecal incontinence). There were no G4 or G5 events. Median follow-up from the time of RC was 21.4 months at the time of data cutoff in 10/2020. Among evaluable pts, 1-year RFS and OS were 71% and 94% while 2-year RFS and OS were 64% and 75%. Conclusions: This prospective trial supports the safety and efficacy of ATZ as neoadjuvant therapy in MIBC. Although pCR and rates of downstaging were lower than what was previously reported in comparable neoadjuvant trials of checkpoint inhibitors in MIBC, pCRs in this trial were seen even in pts receiving only 1-2 doses of ATZ. Many pts had a durable recurrence-free period and all 4 evaluable pts who had pathologic downstaging were alive and disease free at 2 years post RC. Translational and biomarker work from this study is also being pursued. Clinical trial information: NCT02451423.

Implementation of clinician-facing prostate cancer therapeutic clinical trial decision tool at a comprehensive cancer center

19

Background: The conventional model for clinical trial (CT) recruitment relies on clinicians to identify potential CTs for patients. Internet technology can be leveraged as a decision tool to enhance the CT recruitment process. Methods: An internet-based, clinician-facing decision tool was developed in genitourinary medical oncology clinic at a Comprehensive Cancer Center (CCC). The tool provided access to a real-time, tailored list of treatment CTs actively recruiting patients with PCa at the CCC based on clinical characteristics inputted by user. The clinical data was summarized. All clinicians (n = 9) with access to the decision tool completed a survey to assess effectiveness and satisfaction. Results: During a 9-month pilot period, user engagement increased from a baseline of 36 to 136 cases per month, with a total of 644 cases overall. Among cases, 525 had metastatic disease, 436 of which were metastatic castration resistant PCa (mCRPC). Overall, 145 cases were classified as having oligo-metastatic ( < = 3) PCa, 93 of whom were also mCRPC. Prior treatments received included abiraterone in hormone-sensitive PCa (HSPC 19.3%, CRPC 48.7%); enzalutamide (HSPC 3.7%, CRPC 34.9%) apalutamide (HSPC 1.3%, CRPC 6.9%), taxane (HSPC 17.2%, CRPC 27.8%), radium-223 (6.1%), sipuleucel-T (18.3%), parp inhibitors (4%), or check-point inhibitors (6%). Clinician-inputted genomics of cases included CDK12 (20.9%), MSI-high disease (13.6%), BRCA1/2 (32.7%), ARID1a (7.3%), ATM (21.8%), FANCA (4.5%), or CHEK2 (6.4%) and HDAC2 (0.9%). Among survey respondents, use of tool in clinic was reported sometimes (22%), often/always (78%). Results of decision tool were reported to inform treatment sometimes (22%) or often/always (78%). Respondents confidence in often/always knowing all available CTs increased from a baseline of 0% to 89%, and 89% of users reported very/complete satisfaction with decision tool. Conclusions: An internet-based CT decision tool for provides detailed clinical characteristics of patients for whom CTs are being considered at a CCC. Clinicians using the decision tool report high levels of satisfaction. The tool was effective in increasing confidence in knowledge of current available CTs. Data gathered in the decision tool may inform future CT development. Future research with expanded use of decision tool among referring clinicians will assess its impact in promoting diversity among CT participants.

Feasibility study of gallium-68 citrate PET as a bone-tropic imaging biomarker in mCRPC

31

Background: Transferrin receptor (TFRC) expression is controlled by the PI3K and MYC signaling pathways, which are frequently dysregulated in prostate cancer (PC). Gallium-68 citrate (68Ga-citrate) is an iron biomimetic, which can be used to image PC in a TFRC dependent fashion. We performed a single-center pilot imaging study to investigate the use of 68Ga-citrate PET in patients with metastatic castration-resistant PC (mCRPC). Methods: Following written informed consent, mCRPC patients were prospectively enrolled and underwent 68Ga-citrate PET imaging. Optional metastatic tumor biopsies were undertaken at the time of imaging. Results: 34 mCRPC patients underwent 68Ga-citrate PET imaging. The median age was 67.5 years old. Median duration of castration resistance was 17.5 months; 14.7% of patients were post-docetaxel. Median serum PSA was 35.2 ng/dL. A total of 483 lesions were detected on conventional imaging (CT, 99mTc-HDP) or 68Ga-citrate PET, including 420 osseous and 63 soft tissue (nodal and visceral) lesions (Table). 67.3% of all lesions were detected on 68Ga-citrate PET, including 74.5% of all osseous lesions but only 19.0% of all soft tissue lesions (p<0.0001). Eight (1.7%) lesions were detected on 68Ga-citrate PET imaging only. Per-lesion average SUVmax (SUVmax,avg) was 6.7. Metastatic biopsies of PET avid lesions were performed in 20 patients (59%); adenocarcinoma histology was confirmed in 14 (70%) cases, treatment-emergent small cell neuroendocrine cancer (t-SCNC) in 6 (30%). There was no significant difference in SUVmax,avg between patients with adenocarcinoma or t-SCNC (SUVmax,avg 7.3 vs 7.6, respectively; Table). Serial 68Ga-citrate PET perfomed in a patient with biopsy-confirmed t-SCNC after 2 cycles of carboplatin/cabazitaxel demonstrated an early metabolic response (28.5% decrease in average SUVmax) confirmed on subsequent conventional imaging. Conclusions: 68Ga-citrate PET detects mCRPC bone metastases in patients with biopsy-proven prostatic adenocarcinoma or t-SCNC, distinguishing it from lineage dependent agents such as PSMA tracers. Detection of an early metabolic response in the bone of a treated t-SCNC patient was observed. Further prospective studies are ongoing coupling serial Ga-citrate PET with investigational agents targeting the MYC signaling pathway. Clinical trial information: NCT02391025. [Table: see text]

Heterogeneity in Nectin-4 expression across molecular subtypes of urothelial cancer mediates sensitivity to enfortumab vedotin

463

Background: Enfortumab vedotin (EV) is an antibody-drug conjugate (ADC) targeting Nectin-4 (encoded by the PVRL4/NECTIN4 gene ) approved for treatment-refractory metastatic urothelial cancer. Factors that mediate sensitivity or resistance to EV are unknown. In the present study, we sought to 1) examine heterogeneity of NECTIN4 gene expression across molecular subtypes of bladder cancer and 2) determine if Nectin-4 expression mediates EV sensitivity or resistance. Methods: NECTIN4 expression data from seven muscle-invasive bladder cancer clinical cohorts (n = 1912 total patients) were used to compare relative NECTIN4 expression across molecular subtypes. The outcome of the gene expression analysis was relative NECTIN4 expression in the consensus molecular subtypes of bladder cancer. Expression of NECTIN4 was validated in multiple bladder cancer cell lines. NECTIN4 was stably over-expressed or knocked down in basal (TCCSUP and UMUC-3) and luminal (HT-1376, HT-1197 and UMUC-9) bladder cancer cell lines, respectively, and EV dose-response assays were performed, as measured by cell proliferation and clonogenic assays. Results: NECTIN4 expression is heterogenous across molecular subtypes of bladder cancer and significantly enriched in luminal subtypes (p < 0.001). NECTIN4 expression is positively correlated with the luminal markers GATA3, FOXA1, and PPARG across cohorts (Spearman’s rank correlation r = 0.57, p < 0.0001 for GATA3, r = 0.37, p < 0.0001 for FOXA1, and r = 0.56, p < 0.0001 for PPARG). NECTIN4 expression is both necessary and sufficient for EV sensitivity in luminal and basal subtypes of urothelial bladder cancer cells. Downregulation of NECTIN4 led to EV resistance, and EV-resistant cell lines expressed decreased levels of Nectin-4. Conclusions: Results of this pre-clinical study suggest that sensitivity to EV is mediated by expression of NECTIN4, which is significantly enriched in luminal subtypes of bladder cancer. Downregulation of NECTIN4 leads to resistance to EV. These findings have implications for biomarker development, patient selection and the inclusion of molecular subtyping in ongoing and future EV clinical trials. Further investigation into Nectin-4 loss as a mechanism of resistance in patients treated on EV is warranted.

TERT promoter mutation as a prognostic marker in patients with advanced urothelial carcinoma treated with immune checkpoint inhibitors

476

Background: Reliable predictive markers are lacking in patients (pts) with locally advanced or metastatic urothelial carcinoma (aUC) treated with immune checkpoint inhibitors (ICI). We sought to determine whether specific genomic alterations could be used to predict overall survival (OS) in this patient population. Methods: We undertook a retrospective cohort study of pts with aUC who received ICI and underwent genomic profiling by next-generation sequencing (NGS). All patients underwent NGS using commercially available platforms (e.g. Foundation Medicine, Strata, Invitae), or testing on the CLIA-certified institutional panel UCSF500. Associations between the 20 most frequently altered genes and OS were first examined by Cox regression. Genes with a p <0.1 on univariate analysis and relevant clinical variables were then included in a multivariable analysis. Results: We identified 78 pts treated with ICI for aUC with available genomic profiling results. Median age at ICI initiation was 71; the majority of patients had visceral metastases (70.5%), ECOG performance status ≤1 (62.8%) and received ICI in the post-platinum setting (52.6%). Objective response rate in this cohort was 35.9%, median progression free survival was 4.0 months (95% CI 2.6-10.5) and median OS was 17.5 months (95% CI 14.1-NR) from ICI start. The most commonly altered genes were the TERT promoter (TERTp) (61%), TP53 (52%), RB1 (31%), CDKN2A(29%) and CDKN2B (27%). On univariable analysis there was a trend towards longer OS in pts with TERTp mutations (HR 0.53, 95% CI 0.27-1.06, p = 0.07), and shorter OS in pts with CDKN2B mutations (HR 1.91, 95% CI 0.98-3.73, p = 0.06). Both mutations were included in a multivariable analysis. After adjusting for known prognostic variables (ECOG PS, visceral metastases, albumin, hemoglobin, body mass index [BMI], neutrophil to lymphocyte ratio [NLR], and histology), the presence of a TERTp mutation was significantly associated with improved OS (HR 0.30, 95% CI 0.10-0.93, p = 0.04; Table). Conclusions: The presence of a TERTp mutation was an independent predictor of improved OS in a cohort of aUC pts treated with ICI. Other common mutations and clinical variables were not associated with OS on a multivariable analysis. These findings are hypothesis-generating and prospective validation is needed. [Table: see text]

Molecular Insights in Transmission of Cancer From an Organ Donor to Four Transplant Recipients

Organ donors are systematically screened for infection, whereas screening for malignancy is less rigorous. The true incidence of donor-transmitted malignancies is unknown due to a lack of universal tumor testing in the posttransplant setting. Donor-transmitted malignancy may occur even when not suspected based on donor or recipient factors, including age and time to cancer diagnosis. We describe the detection of a gastrointestinal adenocarcinoma transmitted from a young donor to 4 transplant recipients. Multidimensional histopathologic and genomic profiling showed a CDH1 mutation and MET amplification, consistent with gastric origin. At the time of writing, one patient in this series remains alive and without evidence of cancer after prompt organ explant after cancer was reported in other recipients. Because identification of a donor-derived malignancy changes management, our recommendation is to routinely perform short tandem repeat testing (or a comparable assay) immediately upon diagnosis of cancer in any organ transplant recipient. Routine testing for a donor-origin cancer and centralized reporting of outcomes are necessary to establish a robust evidence base for the future development of clinical practice guidelines.

A machine learning approach to optimizing cell-free DNA sequencing panels: with an application to prostate cancer

BACKGROUND

Cell-free DNA's (cfDNA) use as a biomarker in cancer is challenging due to genetic heterogeneity of malignancies and rarity of tumor-derived molecules. Here we describe and demonstrate a novel machine-learning guided panel design strategy for improving the detection of tumor variants in cfDNA. Using this approach, we first generated a model to classify and score candidate variants for inclusion on a prostate cancer targeted sequencing panel. We then used this panel to screen tumor variants from prostate cancer patients with localized disease in both in silico and hybrid capture settings.

METHODS

Whole Genome Sequence (WGS) data from 550 prostate tumors was analyzed to build a targeted sequencing panel of single point and small (< 200 bp) indel mutations, which was subsequently screened in silico against prostate tumor sequences from 5 patients to assess performance against commonly used alternative panel designs. The panel's ability to detect tumor-derived cfDNA variants was then assessed using prospectively collected cfDNA and tumor foci from a test set 18 prostate cancer patients with localized disease undergoing radical proctectomy.

RESULTS

The panel generated from this approach identified as top candidates mutations in known driver genes (e.g. HRAS) and prostate cancer related transcription factor binding sites (e.g. MYC, AR). It outperformed two commonly used designs in detecting somatic mutations found in the cfDNA of 5 prostate cancer patients when analyzed in an in silico setting. Additionally, hybrid capture and 2500X sequencing of cfDNA molecules using the panel resulted in detection of tumor variants in all 18 patients of a test set, where 15 of the 18 patients had detected variants found in multiple foci.

CONCLUSION

Machine learning-prioritized targeted sequencing panels may prove useful for broad and sensitive variant detection in the cfDNA of heterogeneous diseases. This strategy has implications for disease detection and monitoring when applied to the cfDNA isolated from prostate cancer patients.

Pharmacokinetics, Safety, and Antitumor Effect of Apalutamide with Abiraterone Acetate plus Prednisone in Metastatic Castration-Resistant Prostate Cancer: Phase Ib Study

PURPOSE

Apalutamide is a next-generation androgen receptor (AR) inhibitor approved for patients with nonmetastatic castration-resistant prostate cancer (CRPC) and metastatic castration-sensitive prostate cancer. We evaluated the pharmacokinetics, safety, and antitumor activity of apalutamide combined with abiraterone acetate plus prednisone (AA-P) in patients with metastatic CRPC (mCRPC).

PATIENTS AND METHODS

Multicenter, open-label, phase Ib drug-drug interaction study conducted in 57 patients with mCRPC treated with 1,000 mg abiraterone acetate plus 10 mg prednisone daily beginning on cycle 1 day 1 (C1D1) and 240 mg apalutamide daily starting on C1D8 in 28-day cycles. Serial blood samples for pharmacokinetic analysis were collected on C1D7 and C2D8.

RESULTS

Systemic exposure to abiraterone, prednisone, and prednisolone decreased 14%, 61%, and 42%, respectively, when apalutamide was coadministered with AA-P. No increase in mineralocorticoid excess-related adverse events was observed. Patients without prior exposure to AR signaling inhibitors had longer median treatment duration and greater mean decrease in prostate-specific antigen (PSA) from baseline compared with those who had received prior therapy. Confirmed PSA reductions of ≥50% from baseline at any time were observed in 80% (12/15) of AR signaling inhibitor-naïve patients and 14% (6/42) of AR signaling inhibitor-treated patients.

CONCLUSIONS

Treatment with apalutamide plus AA-P was well tolerated and showed evidence of antitumor activity in patients with mCRPC, including those with disease progression on AR signaling inhibitors. No clinically significant pharmacokinetic interaction was observed between abiraterone and apalutamide; however, apalutamide decreased exposure to prednisone. These data support development of 1,000 mg abiraterone acetate plus 10 mg prednisone daily with 240 mg apalutamide daily in patients with mCRPC.

Intratumoral CD4+ T Cells Mediate Anti-tumor Cytotoxicity in Human Bladder Cancer

Responses to anti-PD-1 immunotherapy occur but are infrequent in bladder cancer. The specific T cells that mediate tumor rejection are unknown. T cells from human bladder tumors and non-malignant tissue were assessed with single-cell RNA and paired T cell receptor (TCR) sequencing of 30,604 T cells from 7 patients. We find that the states and repertoires of CD8⁺ T cells are not distinct in tumors compared with non-malignant tissues. In contrast, single-cell analysis of CD4⁺ T cells demonstrates several tumor-specific states, including multiple distinct states of regulatory T cells. Surprisingly, we also find multiple cytotoxic CD4⁺ T cell states that are clonally expanded. These CD4⁺ T cells can kill autologous tumors in an MHC class II-dependent fashion and are suppressed by regulatory T cells. Further, a gene signature of cytotoxic CD4⁺ T cells in tumors predicts a clinical response in 244 metastatic bladder cancer patients treated with anti-PD-L1.

Study EV-103: Durability results of enfortumab vedotin plus pembrolizumab for locally advanced or metastatic urothelial carcinoma

5044

Background: Platinum chemotherapy is the standard for patients (pts) with metastatic urothelial carcinoma (mUC) in the first line (1L) setting. PD-1/PD-L1 inhibitors, such as pembrolizumab (P), have shown promising durability in this setting for PD-L1 high patients. Enfortumab vedotin (EV) is an antibody-drug conjugate that delivers the microtubule-disrupting agent MMAE to cells expressing Nectin-4, which is highly expressed in UC. EV recently received FDA accelerated approval based on tumor response rates for adults with locally advanced or mUC who have previously received a PD-1/PD-L1 inhibitor and a platinum-containing chemotherapy. EV is investigational in the 1L setting. Initial EV + P data were previously presented (Hoimes ESMO 2019); this provides durability data and an update on safety/ORR. Methods: This multicohort study (NCT03288545) evaluated the safety/activity of EV + P. We report a cohort of 1L cisplatin-ineligible patients treated with EV 1.25 mg/kg + P. In each 3-week cycle, EV was administered on Days 1 and 8 and P on Day 1. The primary endpoint was safety/tolerability; secondary objectives included determination of recommended EV dose, ORR, DCR, DOR/PFS per RECIST v1.1, and OS. Results: As of 8 Oct 2019, 45 1L or previously untreated mUC pts (median age 69 yr [51–90]) received a median of 9 (range 1-22) cycles of EV + P. The most common treatment-emergent adverse events (AE) were fatigue (58%, 11% ≥G3), alopecia (53%), and peripheral sensory neuropathy (53%, 4% ≥G3). One pt died due to an AE reported as related (multiple organ failure). With a median follow-up of 11.5 mo, confirmed investigator-assessed ORR was 73.3% (95% CI, 58.1, 85.4) including 15.6% CRs; DCR was 93.3%. The ORR in pts with liver metastasis was 53.3% (8/15). The ORR in pts with available PD-L1 status was 78.6% in PD-L1 high (11/14) and 63.2% in PD-L1 low (12/19). Of the 33 responders, 18 (55%) have ongoing responses including 11 responses beyond 10 months. The median DOR was not reached (range 1.2 to 12.9+ mo); the 12-month DOR rate was 53.7% (95% CI, 27.4, 74.1). The median PFS was 12.3 mo (95% CI, 7.98, -); the 12-month PFS rate was 50.1% (95% CI, 33.0, 65.0). The median OS was not reached (range 0.66 to 19.2+ mo); the 12-month OS rate was 81.6% (95% CI, 62.0, 91.8). Conclusions: In 1L cisplatin-ineligible pts with mUC, EV + P, a potential platinum free option, demonstrates promising activity and durability, with a manageable safety profile. Further evaluation of EV + P in mUC and muscle-invasive UC is ongoing. Clinical trial information: NCT03288545 .

Correlation of tumor mutational burden (TMB) with molecular profiling and clinical characteristics in patients with bladder cancer

e17025

Background: Bladder cancers (BC) are frequently highly mutated. Next generation sequencing (NGS) can both shed light on mutational burden and the specific alterations that provide insights into the underlying biology of individual tumors. Methods: We retrospectively reviewed BC cases assessed with UCSF500, an institutional NGS assay that uses hybrid capture enrichment of target DNA to interrogate approximately 500 frequently mutated cancer genes. Hypermutated tumors were defined as having TMB > 10 mutations/Mb. Fisher’s exact test was used to compare patients (pts) with hypermutated (HM) and non-hypermutated (NHM) tumors. Results: From 2015 to 2019, 74 pts with BC underwent UCSF500 testing; 48 pts were evaluable for TMB, of which 19 pts (40%) had HM tumors. 17/19 pts were evaluable for mutational signatures; all 17 had APOBEC signatures. Signatures were not assessed in NHM tumors due to low TMB. Clinicopathologic characteristics and most common alterations in the two groups are listed in the table. More HM pts had responses to immunotherapy (IO) treatment (86% vs 40%, p = 0.13). Conclusions: In this single-institution BC cohort, HM tumors were common and APOBEC mutational signature was the common underlying biology in HM tumors. There were relevant differences in common alterations between HM and NHM tumors, including more FGFR3 mutations in NHM tumors. HM status and APOBEC signature were suggested as relevant predictive biomarkers of response to IO, which should be investigated further in larger BC cohorts. [Table: see text]

Study EV-103: New randomized cohort testing enfortumab vedotin as monotherapy or in combination with pembrolizumab in locally advanced or metastatic urothelial cancer

TPS5092

Background: Cisplatin-based chemotherapy is the standard for first-line (1L) patients (pts) with locally advanced/metastatic urothelial cancer (LA/mUC). PD-1/PD-L1 inhibitors have promising durability of responses but 1L use is restricted to pts ineligible for cisplatin-containing therapy and whose tumors express PD-L1 (CPS ≥10) or pts ineligible for platinum-containing chemotherapy regardless of PD-L1 status. Enfortumab vedotin (EV), an antibody-drug conjugate, delivers the microtubule-disrupting agent monomethyl auristatin E to cells expressing Nectin-4, which is highly expressed in UC. EV recently received FDA accelerated approval based on tumor response rates for adults with LA/mUC who have previously received a PD-1/PD-L1 inhibitor and a platinum-containing chemotherapy. In the ongoing phase 1b/2 study EV-103/KEYNOTE-869 (NCT03288545), the safety and antitumor activity of EV are investigated as monotherapy (mono) (for the first time in the 1L setting) and in combination with PD-1 inhibitor pembrolizumab (P) +/- chemotherapy in UC. An initial analysis of EV (1.25 mg/kg) + P (200 mg) (both drugs in investigational use here) in this study showed a 73.3% confirmed ORR in 45 1L cisplatin-ineligible LA/mUC pts (dose-escalation + expansion Cohort A) (Rosenberg ASCO 2020). Methods: A new Cohort K randomized 1:1 to 1.25 mg/kg EV mono or 1.25 mg/kg EV + 200 mg P provides additional information on EV + P and the contribution of activity from EV in cisplatin-ineligible pts with LA/mUC in the 1L setting. This cohort will enroll 150 adults (≥18 years) with LA/mUC and measurable disease per RECIST v1.1, and exclude pts with prior systemic treatment for LA/mUC, active CNS metastases, ongoing sensory or motor neuropathy (Grade ≥2), or uncontrolled diabetes. Cisplatin-ineligibility in this study is based on ≥1 of the following: ECOG of 2, creatinine clearance of ≥30 and < 60 mL/min, or hearing loss/dysfunction. In each 3-week cycle of this study, EV is administered on days 1 and 8, and P on day 1. The primary endpoint is ORR per RECIST v1.1 by BICR. Secondary endpoints include ORR per RECIST v1.1 by investigator assessment, DOR, DCR, PFS per RECIST v1.1 by BICR and investigator assessment, OS, safety, and tolerability. Sample size is not based on power calculation for formal hypothesis testing but is selected based on ORR estimate precision based on 95% CIs. Efficacy is summarized by treatment arm with no formal statistical comparisons between arms. The study opened in Oct 2017. Cohort K opened in Jan 2020. Clinical trial information: NCT03288545 .

Efficacy of immune checkpoint inhibitors (ICIs) in rare histological variants of bladder cancer

502

Background: ICIs are effective agents in metastatic urothelial carcinoma in both platinum-refractory and frontline settings. Responses in patients (pts) with non-urothelial histological variants are not well defined. Methods: We undertook a retrospective analysis of pts with metastatic bladder cancer treated with ICI monotherapy. Pts were identified as having a variant histology if any non-urothelial component was present. Fisher’s exact test was used to assess differences in ORR by histology. Results: Between 12/2014 and 10/2019, 102 pts received ICI monotherapy, of whom 93 were evaluable for response and 33 had variant histology. Median age was 70 yrs, 66% were male, 50% received prior platinum-based chemotherapy. Most received pembrolizumab (66%) or atezolizumab (33%). ORR in the overall cohort was 26% (15% PR, 11% CR), with 12% having SD. Histology breakdown and responses are shown in Table. Although twice as many responses were seen in urothelial pts as in pts with variant histologies (ORR 31% vs 15%), this difference was non-significant (p = 0.14). Conclusions: In this large single-institution cohort, ORR in a heterogeneous population of bladder cancer pts was consistent with data previously reported in clinical trials. Pts with variant histologies had numerically lower responses relative to pure urothelial histology, but this difference was not statistically significant. Clinical benefit to ICIs was seen across multiple variant histologies suggesting potential efficacy in this patient population that should be confirmed prospectively.[Table: see text]

Treatment outcomes in metastatic prostate cancer patients with DNA damage repair mutations

187

Background: DNA damage repair mutations (DDM) are common in prostate cancer (PCa). Optimal treatment sequence and outcomes of androgen signaling inhibitors (ASIs) and chemotherapy in this population are unclear. Methods: A retrospective, single-institution study of patients (pts) with mPCa and DDM detected on next-generation sequencing between January 2016 and July 2019 was conducted. For pts with metastatic castration-resistant prostate cancer (mCRPC), chi-squared and Wilcoxon sum rank tests were used to compare PSA50 and Time to Next Treatment (TNT) among different treatment groups, respectively. Results: Among 70 pts with mPCa and DDM, the most common mutations were BRCA2 (24, 27%), ATM (20, 22%), CDK12 (19, 21%), and MLH1/MSH2/MSH6/PMS2 (10, 11%). Fifty-seven pts (81%) received systemic treatment for mCRPC and 68% received ≥3 mCRPC treatments. Among 57 pts with ≥1 mCRPC treatment, 19 (33%) received first abiraterone, and 18 (32%) first enzalutamide. There was a trend toward higher PSA50 (74% vs 47%, P=0.196) and longer TNT (55 vs 34 wk, P=0.286) with first abiraterone vs enzalutamide. Upon switching between ASIs, 0 of 10 pts had a PSA50 response. When given chemotherapy at any point during CRPC treatment, 16/27 (59%) pts had a PSA50 response to docetaxel alone and/or cabazitaxel alone, and 14/24 (58%) to carboplatin-based regimens. Conclusions: To our knowledge, this is the largest single-institution cohort providing real-world treatment data for pts with mPCa and DDM. In the frontline mCRPC setting, abiraterone had a trend suggesting increased activity over enzalutamide that was not statistically significant. Switching ASIs at progression produced no additional responses, suggesting cross-resistance. Responses to taxanes were similar to previously reported data in all-comers. Validation in a larger, prospective cohort is needed to confirm these preliminary findings.

Study EV-103: Preliminary durability results of enfortumab vedotin plus pembrolizumab for locally advanced or metastatic urothelial carcinoma

441

Background: Platinum chemotherapy is the standard for patients (pts) with metastatic urothelial carcinoma (mUC) in the first line (1L) setting. In cisplatin-ineligible pts, gem/carbo is a standard therapy, but is poorly tolerated with limited durability and survival. PD-1/PD-L1 inhibitors, such as pembrolizumab (P), have shown promising durability in this setting for PD-L1 high patients. Enfortumab vedotin (EV) is an antibody-drug conjugate that delivers the microtubule-disrupting agent MMAE to cells expressing Nectin-4, which is highly expressed in UC. EV has shown activity in previously treated mUC. Initial EV + P data were previously presented (Hoimes ESMO 2019); this provides first durability data and an update on safety/ORR. Methods: This multicohort study (NCT03288545) evaluated the safety/activity of EV + P. We report a cohort of 1L cis-ineligible patients treated with EV 1.25 mg/kg + P. In each 3-week cycle, EV was administered on Days 1 and 8 and P on Day 1. The primary endpoint was safety/tolerability; secondary objectives included determination of recommended EV dose, ORR, DCR, DOR/PFS per RECIST v1.1, and OS. Results: As of 8 Oct 2019, 45 mUC pts (median age 69 yr [51–90]) received a median of 9 (range 1-22) cycles of EV + P. The most common treatment-emergent adverse events (AE) were fatigue (58%, 11% ≥G3), alopecia (53%), and peripheral sensory neuropathy (53%, 4% ≥G3). One pt died due to an AE reported as related (multiple organ failure). With a median follow-up of 11.5 mo, confirmed investigator-assessed ORR was 73.3% (95% CI, 58.1, 85.4) including 15.6% CRs; DCR was 93.3%. The ORR in pts with liver metastasis was 53.3% (8/15). The ORR in pts with available PD-L1 status was 78.6% in PD-L1 high (11/14) and 63.2% in PD-L1 low (12/19). Of the 33 responders, 18 (55%) have ongoing responses including 11 responses beyond 10 months. The median DOR was not reached (range 1.2 to 12.9+ mo). The median PFS was 12.3 mo (95% CI, 7.98, -). Conclusions: In 1L cis-ineligible pts with mUC, EV + P, a potential platinum free option, demonstrates promising activity and durability, with a manageable safety profile. Further evaluation of EV + P in mUC and muscle-invasive UC is ongoing. Clinical trial information: NCT03288545.

Molecular characterization of a gastric cancer transmitted from an organ donor to four transplant recipients

414

Background: Donor-derived malignancy may occur even when not suspected based on donor or recipient factors, including age and time to cancer diagnosis. Early recognition of donor-derived malignancy has treatment implications. We describe the molecular characterization of a gastric cancer transmitted from an organ donor to heart, liver (LR), left kidney (LKR), and right kidney-pancreas (KPR) recipients. Methods: IRB approval for chart review was obtained; LR, LKR, and KPR also provided research consent for molecular profiling. Short Tandem Repeat (STR) genotyping was performed by polymerase chain reaction and gel electrophoresis. Tumor and germline DNA from patients and the organ donor were subjected to next generation sequencing (NGS) of 479 genes. Fluorescence in situ hybridization (FISH) was used to confirm MET amplification. Results: Donor origin was established by STR analysis, with the tumors showing high levels of donor alleles. Pathology revealed a poorly differentiated adenocarcinoma with signet ring features. Immunohistochemical staining and CA-19-9 elevation were most consistent with gastric or pancreas origin. Tumor sequencing was notable for somatic mutation of CDH1, MET amplification and wild-type KRAS genes. Tumors from LR and KPR were nearly identical based on pathogenic variants, allele frequency, and copy number variation. Insufficient tumor cellularity in all LKR specimens precluded NGS profiling, but clinical testing found that the cancer was mismatch repair proficient; ERBB2 equivocal; and PDL-1 positive. A circulating tumor DNA test did not uncover any genomic alterations; however, MET amplification was confirmed in this tumor using FISH probes. Conclusions: STR analysis and reporting should be standard immediately following diagnosis of cancer in an organ transplant recipient to ascertain donor derivation. Further molecular characterization, including NGS, may aid in defining primary tumor origin. Here, diagnosis with PDL1-positive gastric cancer enabled use of pembrolizumab. One patient remains alive and without evidence of cancer following prompt organ explant after cancer was reported in other recipients.

Prevalence of PD-L1 expression in first-line (1L) locally advanced/unresectable or metastatic urothelial carcinoma (UC)

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Background: Treatments for 1L advanced/metastatic UC include platinum-based chemotherapy, an immune checkpoint inhibitor (ICI) or clinical trial enrollment. Not all patients benefit from, or are eligible for, specific therapies due to comorbidities and performance status. There is an urgent need for biomarker-directed strategies to enable patient selection and improve outcomes. Currently the only clinically used molecular biomarker is PD-L1 protein expression in tumor tissue. Although inconsistent and variable among assays, higher PD-L1 expression generally correlates with increased ICI response rate. Improved understanding of the prevalence and potential prognostic and/or predictive role of PD-L1 can further enhance its clinical utility and guide novel clinical trial designs. Methods: This observational study will enroll 250 patients with advanced UC prior to starting or during 1L therapy, as initiated at the discretion of participating clinicians, from 60 US community sites. The primary endpoint is prevalence of PD-L1 expression by VENTANA SP263 Assay (exact [Clopper-Pearson] 95% CI) on pre-treatment tumor tissue. Secondary endpoints include the association of pre-treatment PD-L1 expression with pre-treatment tumor tissue mutational burden (tTMB), descriptions of treatment response and outcomes (ORR based on RECIST 1.1, PFS, OS) and assessment of their correlations with PD-L1 expression. Exploratory endpoints include the association of pre-treatment tumor tissue PD-L1 with pre-treatment blood-based tumor mutational burden (bTMB), changes in circulating tumor DNA (ctDNA) levels at various timepoints, the correlation between tTMB and bTMB values, and the association of those biomarkers for outcomes of PFS and OS. Enrollment will take place over 24 months with follow-up to 30 months from study enrollment. With 250 patients, the 95% CI for 30%, 45%, and 60% observed prevalence of PD-L1 high are (24.4%, 36.1%), (38.9%, 51.2%), and (53.6%, 66.1%), respectively; the various secondary and exploratory analyses will be descriptive.

A multidisciplinary team-based approach to mitigate the impact of androgen deprivation therapy in prostate cancer: A randomized phase II study

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Background: Androgen deprivation therapy (ADT) is associated with numerous metabolic toxicities that are potentially modifiable. We sought to evaluate the impact of participation in a multidisciplinary clinic (MDC) designed to provide individualized lifestyle modification and management of ADT-related side effects. Methods: This phase II study recruited men with prostate cancer who had started ADT < 6 months prior to enrollment, and in whom ADT was planned for at least 12 months following enrollment. Patients were randomized in a 1:1 ratio to either the MDC or standard of care (SOC). Patients randomized to the MDC were provided monthly multidisciplinary assessment and counseling on exercise, nutrition, and symptom management for 12 months on a rotating schedule. Endpoints included feasibility endpoints (proportion of visits completed), and efficacy endpoints, including mean change from baseline to 12 months in blood pressure (BP), weight, waist circumference, percent body fat, hemoglobin A1C (HbgA1C), insulin resistance, and fasting lipids. Results: 25 men were randomized to MDC, and 23 were randomized to SOC. Overall 91% (295/325) of MDC visits were completed. 72% (18/25) of patients completed all 12 months of MDC, and 80% (20/25) completed the first 6 months. Compared to SOC, patients in the MDC arm had a trend towards more favorable mean percent change from baseline to 12-month follow up in systolic BP (6.5% vs. 10.3%), diastolic BP (-3.9% vs.10.0%), waist circumference (2.5% vs. 4.0%), HbA1C (-2.4% vs. -1.7%), insulin resistance (0.5% vs. 1.9%), and fasting lipids (total cholesterol: 7.0% vs. 21.8%; LDL: -2.9% vs. 7.6%; triglyceride: 15.5% vs. 37.2%). Conclusions: Individualized and comprehensive management of toxicities of ADT in a multidisciplinary clinic is feasible, and appears to provide some benefit over SOC. Larger randomized studies are warranted to investigate whether this intervention will provide lasting benefit. Clinical trial information: NCT02168062.

Circulating cellular biomarkers associated with delayed time to progression among bladder cancer patients treated with immune checkpoint inhibitors

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Background: Circulating tumor cells (CTCs) are an important emerging biomarker in bladder cancer that allow for a minimally invasive assessment of tumor activity and response to treatment. Characterization of CTC and other single cell populations associated with improved clinical outcomes can help guide treatment recommendations for patients with metastatic bladder cancer. Methods: Patients with metastatic bladder cancer who received treatment with anti-PD-1 or anti-PD-L1 agents were enrolled in this study. Patient response to treatment was assessed by treating physicians according to RECIST v1.1. Blood samples were prospectively collected from patients prior to the initiation of therapy and then while on treatment and shipped to Epic Sciences for processing. All nucleated cells were subjected to immunofluorescent (IF) staining and CTC and leukocyte identification by fluorescent scanners using algorithmic analysis. Kaplan-Meier analysis was utilized to compare time to progression of patients whose CTC and leukocyte values were above and below several pre-determined parameters. Results: A total of 27 patients (median age 74 years, 70% male) were enrolled in this study and were treated with anti-PD-1/PD-L1 agents pembrolizumab (n=15), atezolizumab (n=11), or nivolumab (n=1). For 20 patients who had evaluable responses, objective response rate (ORR) was 2/20 (10%), all partial responses; another 5/20 (35%) had stable disease. Increased CD4% (>8% of total leukocytes) was associated with delayed time to progression (TTP) (p=0.002) whereas increased baseline total CTCs (>2) had a statistically non-significant trend towards shorter TTP (p=0.09). Baseline CD8%, CD4/CD8 ratio and CTC PD-L1 status were not associated with TTP. Conclusions: In a preliminary analysis among metastatic bladder cancer patients treated with immune checkpoint inhibitors, patients with an increased baseline CTC count had a statistically non-significant trend towards shorter TTP whereas increased baseline CD4 cells had an association with delayed TTP. This prospective study is ongoing, and the results will be further validated in larger patient cohorts.

Conceptual Framework for Therapeutic Development Beyond Anti-PD-1/PD-L1 in Urothelial Cancer

Platinum-based chemotherapy has been the standard of care in advanced urothelial cancer, but long-term outcomes have remained poor. Immune checkpoint inhibitors, with their favorable toxicity profiles and noteworthy efficacy, have steered a new era in advanced urothelial cancer, with five agents targeting the PD-1/PD-L1 pathway approved by the U.S. Food and Drug Administration (FDA). However, most patients do not achieve response, whereas immunotherapy-related adverse events may cause morbidity, increased health care use, and-rarely-mortality. Therefore, there is an urgent need for additional therapeutic modalities across the disease spectrum. A plethora of clinical trials are ongoing in various disease settings, including chemotherapy regimens, radiotherapy, antibody-drug conjugates, agents targeting additional immune checkpoint pathways, vaccine, cytokines, adoptive cell therapies, as well as targeted and anti-angiogenic agents. Two agents, enfortumab vedotin and erdafitinib, have breakthrough designation by the FDA but are not approved yet (at the time of this paper's preparation). Novel combinations with various treatment modalities and optimal sequencing of active therapies are being investigated in prospective clinical trials. Evaluation of new treatments has met with substantial challenges for many reasons, for example, molecular heterogeneity, clonal evolution, and genomic instability. In the era of precision molecular medicine, and because patients do not respond uniformly to current therapies, there is a growing need for identification and validation of biomarkers that can accurately predict treatment response and assist in patient selection. Here, we review current updates and future directions of experimental therapeutics in urothelial cancer, including examples (but not an exhaustive list) of ongoing clinical trials.

Abstract 4688: Single-cell discrimination of altered human T cell states in the bladder tumor microenvironment

Bladder cancer can be responsive to immunotherapies such as anti-PD-1 and anti-PD-L1 checkpoint inhibitors, but overall response rates are low. Tumor-resident T cells demonstrate considerable heterogeneity as far as antigenic repertoire and phenotype. Whether the bladder tumor environment is enriched for specific types of T cells with a particular functional profile and antigenic specificity, and whether these tumor-specific populations are associated with treatment or response to immunotherapy, remains unclear. We performed single-cell RNA sequencing of CD4+ and CD8+ T cells from localized human bladder tumors and paired adjacent non-malignant bladder. We also assessed resected bladder tumors treated with neoadjuvant chemotherapy or atezolizumab (anti-PD-L1) as part of an ongoing phase II trial. We find both known and unexpected CD4+ T cell functional populations that are specific to the tumor microenvironment, including regulatory T cells and a novel population of cytotoxic CD4+ T cells. Furthermore, by combining whole-transcriptome data with paired T cell receptor identification on single cells, we find that tumor-specific CD4+ populations are clonally expanded and utilize an antigenic repertoire which is distinct from uninvolved bladder. These findings provide evidence for specialization of both phenotype and antigenic specificity of CD4+ T cells in the bladder tumor environment, and indicate that a limited number of tumor-specific antigens may drive in situ expansion and differentiation of specialized CD4+ subsets whose function may be critical to tumor control.

Citation Format: David Yoonsuk Oh, Serena S. Kwek, Serghei Mangul, Siddharth S. Raju, Sasha Targ, Arun Burra, Eric Chow, Dvir Aran, Sima Porten, Maxwell V. Meng, Terence W. Friedlander, Chun Jimmie Ye, Lawrence Fong. Single-cell discrimination of altered human T cell states in the bladder tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4688.