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506 Background: Despite response to systemic therapy, few metastatic urothelial carcinoma (mUC) patients (pts) achieve durable responses. Mutations in the COMPASS-related proteins KMT2D, KMT2C, and KDM6A are found in 66% of UC patients suggesting histone regulation may be an acquired mechanism of tumor viability. We previously found regression of UC in mice when treated with EZH2 inhibitor, tazemetostat. In vivo administration of tazemtostat enhanced the immune response with direct regulation of cytokines and antigen recognition machinery (MHCI and MHCII). We hypothesized that restoration of epigenetic imbalance, combined with immunotherapy, may improve outcomes in mUC pts. Methods: ETCTN 10183 (NCT03854474) is a pilot study evaluating the efficacy of tazemetostat 800 mg BID + pembrolizumab 200 mg every 3 weeks for cisplatin-refractory (Cohort A) or cisplatin/chemo-ineligible advanced UC (Cohort B) pts, with N=12 pts in each cohort. The primary objective is to identify the recommended phase two dose (RP2D) of tazemetostat in combination with pembrolizumab. Secondary objectives include RECIST-based response rate, safety, and progression-free survival. The maximum planned treatment duration is 2 years. Translational objectives include defining total and COMPASS-related genes tumor mutational burden, tumor subtyping, TCR clonality, T cell infiltration, and PDL-1 expression. Results: In the safety lead-in phase, 6 mUC pts were treated. There were no dose-limiting toxicities (DLTs). The RP2D for tazemetostat was established at 800 mg BID. Here we report results of fully accrued cohort A (N=12); 67% males, 33% females, 83% white, 8.3% Black, and 25% Hispanic/Latino ethnicity. The primary sites of UC were: bladder (n=9, 75%), renal pelvis (n=2, 17%), and ureter (n=1, 8.3%). The median (interquartile range, IQR) time since primary diagnosis was 1.1 years (0.7, 1.9); 11/12 patients had non-nodal metastatic disease; 10/12 had 1 or more visceral/bone metastasis. Median number of treatment cycles was 5 (IQR: 3-11; range 1-35). Median duration on protocol treatment was 12 weeks (IQR: 7-30; range 3-107 weeks). Three pts had treatment related grade 3/4 AEs: grade 4 sepsis (n=1), grade 3 lymphopenia (n=2); anemia, increased alkaline-phosphatase, and HSV oral infection (n=1 each). Best response was partial response (PR) in 3 pts (25%) and 3 (25%) had stable disease. Median PFS was 3.1 months (95%CI: 2.3-NA), and median overall survival was 8.0 months (95% CI: 4.7 – NA). Conclusions: The RP2D dose for tazemetostat is 800 mg + 200 mg Pembrolizumab q 3 weeks. The combination was feasible, well tolerated, and resulted in durable responses in poor-risk chemo-refractory UC patients. Clinical trial information: 03854474 .

40 Background: Previously we have reported enrollment disparities in PCa clinical trials. Funding source can influence minority representation in clinical trials. Hence, we aimed to evaluate the impact of source of funding on enrollment disparities in PCa clinical trials. Methods: MEDLINE and EMBASE were searched to identify phase II/III PCa trials. All relevant trials reporting age by 65 years were considered eligible for inclusion. Trials recruiting from the United States (US) were considered eligible for analysis by race and ethnicity. The trial proportions of age, or racial/ethnic subgroup category and the global incidence in the corresponding age subgroup (from the global burden of disease database), or the US-population-based incidence in the corresponding racial/ethnic subgroup (from SEER 21 database) were used to compute enrollment incidence ratio (EIR) at each trial. EIRs with corresponding 95% confidence intervals (CI) were then meta-analyzed using a random-effects model and stratified by sources of funding (industry, US-government, and others [academic and non-US govt]). A univariate meta-regression was conducted to assess the temporal changes in EIR by each funding category. Results: Of 127 trials recruiting from the US, 89 (70%) reported race, and 35 (27%) reported ethnicity. Among those, 57 (64%), 14 (16%), and 18 (20%) trials reported industry, US-government, and other sources of funding, respectively. Of those reporting ethnicity, 23 (66%), 4 (11%), and 8 (23%) trials reported industry, US-government, and other sources of funding, respectively. Among the 287 eligible trials, 49 trials (17%) reported age by 65 years. Of those, 36 (73%), 6 (12%), and 7 (13%) reported industry, US-government, and other sources of funding, respectively. In terms of racial/ethnic enrollment, Black patients were significantly under-represented in industry funded trials (0.33; 0.27-0.41). No significant disparity was observed in US-government funded trials (0.75: 0.57-1.00). The P-value of interaction was <0.0001. Hispanics were significantly under-represented in industry funded clinical trials (0.56; 0.43-0.74). The number of US-government funded trials reporting Hispanics were small (<10) which precluded any meaningful statistics. No significant disparity was observed in terms of older adults (EIR: 1.00; 95% CI: 0.95; 1.05) overall and by funding sources. Black patients’ representation in industry funded PCa trials has significantly decreased over the last three decades. No significant change was observed in US-government funded PCa trials over the last three decades (P:0.004). Conclusions: Black and Hispanic men with PCa are likely to be under-represented in industry sponsored clinical trials. Black patients’ representation in industry sponsored trials has declined over time, thus widening the cancer-care inequities in these patients.

195 Background: Preliminary data suggests that patients with metastatic castration-sensitive prostate cancer (mCSPC) who achieve deep prostate-specific antigen (PSA) response may have improved survival. This finding may have implications for developing treatment de-escalation strategies. Thus, we assessed the overall survival by deep PSA response in mCSPC patients receiving intensified treatments. Methods: MEDLINE and EMBASE were systematically searched from each database’s inception through 1st October 2022. Trials assessing androgen deprivation therapy intensification (doublets, triplets) and reporting overall survival (OS) by deep PSA response were considered eligible for inclusion. Deep PSA response was defined as the PSA level of less than 0.1 or 0.2 ng/ml within eight months after initiation of intensified treatment. Precomputed effect estimates of OS (deep PSA response vs no deep PSA response) were pooled using an inverse-variance approach after logarithmic transformation; a random-effects meta-analysis was conducted within the Bayesian framework using empirical informative priors for heterogeneity parameter as specified by Turner et al. Summary effect was expressed as hazard ratios (HR) with the corresponding 95% credible intervals (CrI). A sensitivity analysis was conducted using the Der Simonian-Lairds random-effects meta-analysis with Hartung-Knapp (HK) adjustment. Results: Five RCTs (PEACE-1, ARASENS, CHAARTED, LATITUDE, TITAN) with 2533 patients were included in this systematic review. A total of 1335 patients experienced a deep PSA response, while 1218 did not achieve a deep PSA response after the initiation of intensified treatment. The pooled incidence of deep PSA response was 49.45% (95% confidence interval: 37.75-61.18). Bayesian meta-analysis showed significantly improved OS in overall mCSPC patient population who achieved a deep PSA response after intensified treatment with either triplet or doublet therapy as compared to those who did not achieve a deep PSA response (HR: 0.39; 95% CI: 0.30-0.50) as shown. The results were consistent with HK adjustment. Conclusions: Excellent overall survival in patients with deep PSA response may offer an opportunity to guide treatment de-escalation trials in carefully selected mCSPC patients. [Table: see text]

193 Background: We maintain a network meta-analysis for the treatment of mCSPC using a living interactive evidence (LIvE) synthesis framework. Recently, the STAMPEDE trial presented evidence regarding a new triplet regimen (enzalutamide-abiraterone-androgen deprivation therapy [E+AAP+ADT]). Hence, in this report we provide the most-up-to-date evidence to inform the choice of optimal therapy in mCSPC patients. Methods: Phase III randomized controlled trials (RCTs) assessing treatment intensification with androgen pathway inhibitors (API), docetaxel (D), or both in patients with mCSPC were included. Mixed treatment comparisons for overall-survival (OS) and progression-free survival (PFS) were made across randomized comparisons using a frequentist network-meta-analysis. Additionally, subgroup data from three trials (ENZAMET, TITAN, ARCHES) by the receipt of docetaxel were abstracted to evaluate the comparative effectiveness of different triplet regimens. Treatment effects were expressed as hazard ratio (HR) and 95% confidence intervals (CI). Relative treatment rankings were evaluated using P-scores and assessed in congruency with the pairwise estimates. Results: This report includes 10 clinical trials (30 references) and over 11500 patients updated as of 1st October 2022. Using randomized data in overall patient population, AAP+D+ADT (rank 1; HR: 0.50; 95% CI: 0.35-0.72) and E+AAP+ADT (rank 4; HR: 0.76; 0.62-0.93) significantly improved PFS compared to D+ADT (rank 7) but not when compared to E+ADT (rank 2) and APA+ADT (rank 3). Similarly, darolutamide (DARO)+D+ADT (rank 1; HR: 0.68; 0.57-0.81), AAP+D+ADT (rank 2; HR: 0.75; 0.59-0.95) significantly improved OS when compared to D+ADT (rank 7). Efficacy by volume of disease and timing of metastatic presentation was consistent with prior update. Using subgroup data by the receipt of docetaxel, a total of five triplet regimens (DARO+D+ADT, AAP+D+ADT, E+D+ADT, apalutamide (APA)+D+ADT, and E+AAP+ADT) were evaluable for comparisons. E+D+ADT (rank 3) improved PFS compared to D+ADT (rank 9; HR: 0.52; 0.41-0.66) and E+AAP+ADT (rank 6; HR: 0.70; 0.52-0.94). Compared to AAP+ADT (rank 7), E+D+ADT (HR: 0.64; 0.49-0.84) and AAP+D+ADT (rank 2; 0.62; 0.42-0.91) significant improved PFS. However, no significant differences were observed among E+D+ADT, AAP+D+ADT, and APA+D+ADT. Similarly, DARO+D+ADT (rank 1) improved OS compared to APA+D+ADT (HR: 0.47; 0.24-0.93). Conclusions: Current evidence favors the use of emerging triplet regimens over docetaxel doublet but not API doublets in overall population. Among different triplets, E+AAP+ADT may not delay progression compared to docetaxel triplets. Hence, access to treatment, toxicity, disease volume and timing of metastases should be carefully considered in mCSPC patients.

116 Background: The impact of socioeconomic status on genitourinary (GU) cancer mortality in the United States (US) is unclear. Hence, we evaluated the association of the socioeconomic status with GU cancer mortality across the US counties. Methods: County-level age-adjusted mortality rates (AAMR) per 100,000 person-years (PY) for populations diagnosed with GU cancers were abstracted from the wide-ranging online data for epidemiological research (WONDER) database. The agency for toxic substances and disease registry (ATSDR) was queried to obtain county-level social vulnerability indices from 2014-2018. Percentile ranking scores (PRS: ranging from 0-1) were computed for each US county and further categorized into quartiles (Q: 1st: 0-0.25 [least vulnerable]; 4th: 0.75-1.00 [most vulnerable]). AAMRs were then linked with quartile rankings. A population-weighted, Poisson regression analysis was conducted to compute rate ratios (RR) of AAMRs between 4th and 1st Q with the corresponding 95% confidence intervals (CI). Results: A total 3142 US counties were included in this analysis. The AAMR for GU cancers was 22.6 overall deaths (OD) and 4.20 premature deaths (PD; defined as death at age <65 years) per 100,000 PY. GU cancer-related mortality increased in a stepwise fashion from the 1st Q to the 4th Q (OD: 21.6 vs 24.1; PD: 3.48 vs 5.19). In terms of OD by specific GU cancers, significantly higher AAMRs were observed in the 4th Q compared to the 1st Q for patients with prostate cancer (RR; 1.19 [95% CI;1.14-1.24]), and renal cell carcinoma (RCC; 1.12 [1.04-1.21]) but not for those with lower urothelial tract cancers (0.92 [0.87-0.96]). Among subgroups, non-Hispanic Blacks (1.19 [1.07-1.33]), and Hispanics (1.28 [1.08-1.51]) with prostate cancer and men with RCC (1.11; 1.03-1.19) in the 4th Q experienced significantly higher overall mortality when compared to those in the 1st Q. With regards to PD, significantly higher AAMRs were observed in the 4th Q vs 1st Q for patients with prostate cancer (1.54 [1.34-1.77]), and RCC (1.28 [1.12-1.45]). Consistently, men with RCC in the 4th Q also experienced higher premature mortality when compared to the 1st Q. Sparsity of mortality data among different ethnic/racial subgroups across the US counties precluded any formal assessment of disparity by specific GU cancers. A sensitivity analysis, conducted using the weighted linear regression approach, showed consistent results. Conclusions: Population level data suggest that socially vulnerable populations, especially Non-Hispanic Black and Hispanic men with prostate cancer, and men with renal cell carcinoma may be at an increased risk of cancer-related mortality. Hence, there is a dire need to address this mortality gap across different socioeconomic subgroups to ensure health-care equity. Investigations at the patient level are required to further ascertain these findings.

Accurate clinical staging of bladder cancer aids in optimizing the process of clinical decision-making, thereby tailoring the effective treatment and management of patients. While several radiomics approaches have been developed to facilitate the process of clinical diagnosis and staging of bladder cancer using grayscale computed tomography (CT) scans, the performances of these models have been low, with little validation and no clear consensus on specific imaging signatures. We propose a hybrid framework comprising pre-trained deep neural networks for feature extraction, in combination with statistical machine learning techniques for classification, which is capable of performing the following classification tasks: (1) bladder cancer tissue vs. normal tissue, (2) muscle-invasive bladder cancer (MIBC) vs. non-muscle-invasive bladder cancer (NMIBC), and (3) post-treatment changes (PTC) vs. MIBC.

Importance The effectiveness of triplet therapy compared with androgen pathway inhibitor (API) doublets in a heterogeneous patient population with metastatic castration-sensitive prostate cancer (mCSPC) is unknown. Objective To assess the comparative effectiveness of contemporary systemic treatment options for patients with mCSPC across clinically relevant subgroups. Data Sources For this systematic review and meta-analysis, Ovid MEDLINE and Embase were searched from each database’s inception (MEDLINE, 1946; Embase, 1974) through June 16, 2021. Subsequently, a “living” auto search was created with weekly updates to identify new evidence as it became available. Study Selection Phase 3 randomized clinical trials (RCTs) assessing first-line treatment options for mCSPC. Data Extraction and Synthesis Two independent reviewers extracted data from eligible RCTs. The comparative effectiveness of different treatment options was assessed with a fixed-effect network meta-analysis. Data were analyzed on July 10, 2022. Main Outcomes and Measures Outcomes of interest included overall survival (OS), progression-free survival (PFS), grade 3 or higher adverse events, and health-related quality of life. Results This report included 10 RCTs with 11 043 patients and 9 unique treatment groups. Median ages of the included population ranged from 63 to 70 years. Current evidence for the overall population suggests that the darolutamide (DARO) triplet (DARO + docetaxel [D] + androgen deprivation therapy [ADT]; hazard ratio [HR], 0.68; 95% CI, 0.57-0.81), as well as the abiraterone (AAP) triplet (AAP + D + ADT; HR, 0.75; 95% CI, 0.59-0.95), are associated with improved OS compared with D doublet (D + ADT) but not compared with API doublets. Among patients with high-volume disease, AAP + D + ADT may improve OS compared with D + ADT (HR, 0.72; 95% CI, 0.55-0.95) but not compared with AAP + ADT, enzalutamide (E) + ADT, and apalutamide (APA) + ADT. For patients with low-volume disease, AAP + D + ADT may not improve OS compared with APA + ADT, AAP + ADT, E + ADT, and D + ADT. Conclusions and Relevance The potential benefit observed with triplet therapy must be interpreted with careful accounting for the volume of disease and the choice of doublet comparisons used in the clinical trials. These findings suggest an equipoise to how triplet regimens compare with API doublet combinations and provide direction for future clinical trials.

ImportanceProstate cancer (PCa) is marked by disparities in clinical outcomes by race, ethnicity, and age. Equitable enrollment in clinical trials is fundamental to promoting health equity.ObjectiveTo evaluate disparities in the inclusion of racial and ethnic minority groups and older adults across PCa clinical trials.Data SourcesMEDLINE, Embase, and ClinicalTrials.gov were searched to identify primary trial reports from each database's inception through February 2021. Global incidence in age subgroups and US population-based incidence in racial and ethnic subgroups were acquired from the Global Burden of Disease and Surveillance, Epidemiology, and End Results 21 incidence databases respectively.Study SelectionAll phase 2/3 randomized PCa clinical trials were eligible for age disparity analyses. Trials recruiting exclusively from the US were eligible for primary racial and ethnic disparity analyses.Data Extraction and SynthesisThis study was reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines. Data were pooled using a random-effects model.Main Outcomes and MeasuresEnrollment incidence ratios (EIRs), trial proportions (TPs) of participants 65 years or older or members of a racial and ethnic subgroup divided by global incidence in the corresponding age group, or US population–based incidence in the corresponding racial and ethnic subgroup, were calculated. Meta-regression was used to explore associations between trial characteristics and EIRs and trends in EIRs during the past 3 decades.ResultsOf 9552 participants among trials reporting race, 954 (10.8%) were African American/Black, 80 (1.5%) were Asian/Pacific Islander, and 8518 (78.5) were White. Of 65 US trials, 45 (69.2%) reported race and only 9 (13.8%) reported data on all 5 US racial categories. Of 286 global trials, 75 (26.2%) reported the enrollment proportion of older adults. Outcomes by race and age were reported in 2 (3.1%) and 41 (15.0%) trials, respectively. Black (EIR, 0.70; 95% CI, 0.59-0.83) and Hispanic (EIR, 0.70; 95% CI, 0.59-0.83) patients were significantly underrepresented in US trials. There was no disparity in older adult representation (TP, 21 143 [71.1%]; EIR, 1.00; 95% CI, 0.95-1.05). The representation of Black patients was lower in larger trials (meta-regression coefficient, −0.06; 95% CI, −0.10 to −0.02; P = .002).Conclusions and RelevanceThe results of this meta-analysis suggest that Black and Hispanic men are underrepresented in trials compared with their share of PCa incidence. The representation of Black patients has consistently remained low during the past 2 decades.

5083 Background: ARASENS and PEACE-1 trials suggests treatment intensification with novel hormonal therapy (NHT) in addition to androgen deprivation therapy (ADT) and docetaxel (DOC) provides survival benefit as compared to DOC+ADT in patients with metastatic castration sensitive prostate cancer (mCSPC). However, the performance of triplet therapy as compared to NHT+ADT remains unexplored. Methods: MEDLINE, EMBASE and recent conference proceedings were searched to include phase III trials evaluating triplet therapy in patients with mCSPC and reporting treatment effects in subgroup of patients with and without docetaxel. Outcomes included overall survival (OS) and radiographic progression free survival (rPFS). Precomputed hazard ratios (HRs) and confidence intervals (CIs) from non-randomized subgroup comparisons were pooled after logarithmic transformation using inverse-variance weighting approach. A DerSimonian-Laird random-effects meta-analysis was then performed to assess subgroup differences. Interaction between subgroups was assessed using P-value of heterogeneity. Mixed treatment comparisons were computed using a fixed-effect model within the frequentist framework using subgroup effect estimates from eligible trials. Results: This meta-analysis included five clinical trials (ARASENS, PEACE-1, ENZAMET, ARCHES and TITAN) with a total of 5804 patients (docetaxel: 2836; no docetaxel: 2836). Subgroup analysis showed statistically significant difference between treatment effects in patients who received docetaxel (NHT + DOC + ADT; HR: 0.74; 95% CI: 0.66-0.84; I2: 0%) and those who did not (NHT + ADT; HR: 0.61; 95% CI: 0.53-0.70; I2: 0%) for OS (p-value of interaction: 0.04). However, no statistically significant interaction was observed in terms of rPFS (p-value: 0.46). Mixed treatment comparisons showed improved OS with NHT + DOC + ADT (HR: 0.74; 95% CI: 0.66-0.84) as compared to DOC + ADT, but not when compared to NHT + ADT (HR: 0.97; 95% CI: 0.78-1.20). NHT + ADT significantly improved OS compared to DOC + ADT (HR: 0.77; 95% CI: 0.64-0.92). Consistently, significant rPFS improvement was observed with NHT + DOC + ADT when compared DOC + ADT (HR: 0.49; 95% CI: 0.42-0.57) but not when compared to NHT + ADT (HR: 0.82; 0.65-1.04). NHT + ADT was observed to improve rPFS compared to DOC + ADT (HR: 0.60; 95% CI: 0.50-0.72). Conclusions: This exploratory and hypothesis generating analysis suggests that addition of docetaxel (triplet therapy) may not delay progression or prolong survival compared to NHT-based doublets. These findings provide direction for future clinical trials in this space and suggest an equipoise to the question of how triplet regimens compare with NHT-doublets. The results should be interpreted with caution as this analysis does not account for potential confounding relationships such as volume of disease.