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Platinum-based chemotherapy has long been the backbone of treatment for urothelial carcinoma. Immune checkpoint inhibitors have revolutionized the treatment paradigm and significantly improved outcomes for many patients. More recently, targeted agents such as erdafitinib and antibody drug conjugates enfortumab vedotin and sacituzumab govitecan have demonstrated robust efficacy after progression on prior chemotherapy and immunotherapy. Many additional agents are currently under investigation in ongoing clinical trials. In this review, we discuss the current treatment landscape, review recent clinical data resulting in approval of novel therapeutic agents and highlight important ongoing studies focusing on the therapeutic landscape beyond immune checkpoint inhibition.

The utilization of neoadjuvant immune checkpoint inhibitor therapy, specifically anti-PD-1/L1 agents, prior to radical cystectomy is an emerging paradigm in muscle-invasive bladder cancer (MIBC). In situ vaccination represents a strategy to manipulate the tumor in order to augment the immune response toward improved local and distant cancer control. The authors describe the study rationale, design and objectives for RAD VACCINE MIBC, a single-arm, single-institution, phase II trial evaluating the efficacy and safety of combination neoadjuvant sasanlimab (humanized IgG monoclonal antibody that targets PD-1) with stereotactic body radiotherapy as an in situ vaccine in cisplatin-ineligible patients with MIBC. The results from this trial will establish the safety profile of this combination strategy and evaluate pathologic complete response rates.

PURPOSE Compared with people living without HIV (PWOH), people living with HIV (PWH) and cancer have traditionally been excluded from immune checkpoint inhibitor (ICI) trials. Furthermore, there is a paucity of real-world data on the use of ICIs in PWH and cancer. METHODS This retrospective study included PWH treated with anti–PD-1- or anti–PD-L1-based therapies for advanced cancers. Kaplan-Meier method was used to estimate overall survival (OS) and progression-free survival (PFS). Objective response rates (ORRs) were measured per RECIST 1.1 or other tumor-specific criteria, whenever feasible. Restricted mean survival time (RMST) was used to compare OS and PFS between matched PWH and PWOH with metastatic NSCLC (mNSCLC). RESULTS Among 390 PWH, median age was 58 years, 85% (n = 331) were males, 36% (n = 138) were Black; 70% (n = 274) received anti–PD-1/anti–PD-L1 monotherapy. Most common cancers were NSCLC (28%, n = 111), hepatocellular carcinoma ([HCC]; 11%, n = 44), and head and neck squamous cell carcinoma (HNSCC; 10%, n = 39). Seventy percent (152/216) had CD4+ T cell counts ≥200 cells/µL, and 94% (179/190) had HIV viral load CONCLUSION Among PWH, ICIs demonstrated differential activity across cancer types with no excess toxicity. Safety and activity of ICIs were similar between matched cohorts of PWH and PWOH with mNSCLC.

Immune-related adverse events (irAE) have been described with immune checkpoint inhibitors (ICI), but the incidence and relative risk (RR) of irAEs associated with these drugs remains unclear. We selected five key irAEs from treatments with approved cytotoxic T-lymphocyte–associated protein 4 (CTLA-4), programmed cell death 1 (PD-1), and programmed death ligand 1 (PD-L1) inhibitors (ipilimumab, nivolumab, or pembrolizumab, and atezolizumab, respectively) to better characterize their safety profile. We performed a meta-analysis of randomized phase II/III immunotherapy trials, with non-ICI control arms, conducted between 1996 and 2016. We calculated the incidence and RR of selected all-grade and high-grade gastrointestinal, liver, skin, endocrine, and pulmonary irAEs across the trials using random-effect models. Twenty-one trials were included, totaling 11,454 patients, of whom 6,528 received an ICI (nivolumab, 1,534; pembrolizumab, 1,522; atezolizumab, 751; and ipilimumab, 2,721) and 4,926 had not. Compared with non-ICI arms, ICIs were associated with more all-grade colitis (RR 7.66, P < 0.001), aspartate aminotransferase (AST) elevation (RR 1.80; P = 0.020), rash (RR 2.50; P = 0.001), hypothyroidism (RR 6.81; P < 0.001), and pneumonitis (RR 4.14; P = 0.012). Rates of high-grade colitis (RR 5.85; P < 0.001) and AST elevation (RR 2.79; P = 0.014) were higher in the ICI arms. Ipilimumab was associated with a higher risk of all-grade rash (P = 0.006) and high-grade colitis (P = 0.021) compared with PD-1/PD-L1 ICIs. Incidence of fatal irAE was < 1%. This meta-analysis offers substantial evidence that ICIs are associated with a small but significant increase in risk of selected all-grade irAEs and high-grade gastrointestinal and liver toxicities. Although fatal irAEs remain rare, AEs should be recognized promptly as early interventions may alleviate future complications. Cancer Immunol Res; 5(4); 312–8. ©2017 AACR.

Supplemtary figure and table legends

4 tables included. FDA Approvals for ICIs. Common Terminology Criteria for Adverse Events V4.0. for selected irAEs. Additional subanalysis.

CONSORT diagram for the phase I/II trial of everolimus with and without BNC105P

Master table of 82 mRCC patients with clinical and transcriptomic Nanostring data

Serial evaluation of circulating tumor DNA may allow noninvasive assessment of drivers of resistance to immune checkpoint inhibitors (ICIs) in advanced urothelial cancer (aUC). We used a novel, amplicon-based next-generation sequencing assay to identify genomic alterations (GAs) pre- and post-therapy in 39 patients with aUC receiving ICI and 6 receiving platinum-based chemotherapy (PBC). One or more GA was seen in 95% and 100% of pre- and post-ICI samples, respectively, commonly in TP53 (54% and 54%), TERT (49% and 59%), and BRCA1/BRCA2 (33% and 33%). Clearance of ≥1 GA was seen in 7 of 9 patients responding to ICI, commonly in TP53 (n = 4), PIK3CA (n = 2), and BRCA1/BRCA2 (n = 2). A new GA was seen in 17 of 20 patients progressing on ICI, frequently in BRCA1/BRCA2 (n = 6), PIK3CA (n = 3), and TP53 (n = 3), which seldom emerged in patients receiving PBC. These findings highlight the potential for longitudinal circulating tumor DNA evaluation in tracking response and resistance to therapy.

TPS590 Background: Maintenance avelumab following stable/responding disease after 4-6 cycles of platinum-based chemotherapy is a conventional first-line therapy for metastatic urothelial carcinoma (mUC). Given the attrition of patients between lines of systemic therapy, there is a role for extending the benefits of maintenance avelumab by combinations with tolerable and active agents. Lurbinectedin (Lurbi) is an alkylating agent and selective inhibitor of oncogenic transcription. Lurbi is approved by the US FDA for treating small cell lung cancer with progression on platinum-based chemotherapy with typical dosing as 3.2 mg/m2 intravenously (IV) every 3 weeks. The activity of lurbi in the presence of DNA damage repair (DDR) alterations, multiple transcriptomic drivers and preclinical synergism with and feasibility of co-administration with immune checkpoint inhibitors (ICI) suggests potential activity of combination lurbi and ICI in mUC. Patients with stable or responding disease following platinum-based chemotherapy are phenotypically selected for deficiencies in DDR. Lurbi may be tolerable in this setting given mostly reversible myelosuppression and no serious non-hematologic toxicities especially neurotoxicity. Thus, the combination of lurbi with maintenance avelumab may warrant evaluation in mUC. Methods: A non-randomized multicenter (Advent Health Cancer Institute, Moffitt Cancer Center) phase II trial (n=36) is designed to evaluate combination avelumab (800 mg IV every 2 weeks) and lurbi (3·2 mg/m2 IV as a 1-h infusion every 4 weeks) for those with stable or responding disease following 4-6 cycles of platinum-based first-line platinum-based chemotherapy for mUC. Therapy is continued till progression of disease, intolerable toxicities or patient decision. Patients are seen for a clinical examination every 4 weeks (1 cycle) with laboratory evaluation every 2 weeks. Radiographic imaging is performed every 8 weeks for 6 months and then every 12 weeks thereafter to assess disease. Premedication for lurbi includes corticosteroids (dexamethasone 8 mg or equivalent) and serotonin antagonists. Mandatory granulocyte-colony stimulating factor (G-CSF) prophylaxis will be administered to all patients. Baseline archival tumor tissue and periodic blood is collected for correlative studies (tumor genomics/PD-L1 expression, circulating tumor DNA and immune markers). Given a median progression-free survival (PFS) with avelumab alone of 3.7 months, an alternative median PFS of 6 months is of interest warranting further development. We will enroll 33 evaluable patients to achieve 90% power at a 1-sided alpha level 0.1 to detect hazard ratio of 0.62. Given ~10% of enrolled patients may be inevaluable, we may enroll up to 36 patients. Clinical trial ID: NCT05574504. Clinical trial information: NCT05574504 .

521 Background: Sacituzumab govitecan (SG) demonstrated an objective response rate (ORR) of 27% and median overall survival (OS) of 10.5 months (Mo) in metastatic urothelial carcinoma (mUC) patients (pts) progressing after platinum-based chemotherapy and PD1/L1 inhibitor, which led to accelerated US FDA approval in this setting. The combination of SG and pembrolizumab is safe and active following platinum-based chemotherapy. Nivolumab (NIVO) 1mg/kg plus Ipilimumab (IPI) 3mg/kg has shown promising activity in post-platinum mUC pts. Given the potential synergism between immunogenic cell death induced by SG and IPI-NIVO, we hypothesized that the combination of SG and IPI-NIVO would be safe and active as a frontline treatment for cisplatin ineligible mUC. Methods: 3+ 3 design was used for the phase I dose escalation of SG at 8 mg/kg and 10 mg/kg dose levels. IPI and NIVO were given at 3mg/kg and1mg/kg (I3+N1) intravenously (IV) every 3 weeks x 4 cycles followed by NIVO 360 mg IV day 1 every 3 weeks. SG was given IV at days 1,8 every 3 weeks The primary endpoint was safety and recommended phase 2 dose (RP2D) based on dose limiting toxicity (DLTs) observed in cycle 1; key secondary endpoints include ORR, DOR, PFS and OS. Key inclusion criteria were ECOG-PS 0-1, cisplatin-ineligibility, treatment naïve, no prior PD1/L1 inhibitor except >3 months earlier for non-metastatic disease. Results: The study has completed the phase I dose escalation after enrolling a total of 9 patients (8 men, 1-woman, median age: 74 years). 6 patients were enrolled at SG 8 mg/kg with 1 DLT, and 3 patients at 10 mg/kg with 2 DLTs. DLTs included grade 3 skin rash (n=2) and grade 3 pneumonitis (n=1). The RP2D of SG was determined to be 8 mg/kg with I3+N1. The most common treatment related adverse events (TRAE) included anemia (66.6%) neutropenia (66.6%), pruritus (66.6%), fatigue (66.6%), diarrhea (66.6%) and lymphopenia (55.5%). 2 patients developed grade 2 infusion reactions to SG. Other grade ≥ 3 TRAE included neutropenia (55.5%), anemia (33.3%), arthralgia (11.1%), and elevated amylase/lipase (11.1%). Both grade 2 pneumonitis and myositis were seen in 1 patient. Of the 9 pts, 6 pts (4 pts at SG dose of 8mg/kg and 2 pts at 10 mg/kg) were considered evaluable for response of whom 4 responded (ORR 66.6%) with 1 complete response and 3 partial responses. Median DOR was 9.2 Mo (range 4.6-12.0); mPFS was 8.8 Mo (95% CI 3.8-NR) and mOS was not reached. Conclusions: The RP2D of SG was identified as 8mg/kg in combination with Ipilimumab 3 mg/kg+ Nivolumab 1 mg/kg as first-line therapy for cisplatin-ineligible mUC. Early signals of promising activity were observed in a small cohort of evaluable pts. The Phase 2 trial is ongoing coupled with exploratory biomarker analyses. Clinical trial information: NCT04863885 .

546 Background: Following radical cystectomy (RC) for muscle-invasive bladder cancer (MIBC), recurrence is suboptimally associated with pathologic stage. A prognostic model that incorporates information from comprehensive genomic and transcriptomic data from germline and tumor tissues will improve the selection of high-risk patients (pts) for adjuvant therapy and tailored surveillance. Methods: Pts with MIBC in TCGA who underwent RC (without neoadjuvant chemotherapy) and with whole exome sequencing (WES) of tumor + normal, and tumor RNA-Seq were eligible. Germline variants were called and annotated using GATK4 and Variant Effect Predictor (VEP). Only high and moderate VEP-Impact variants contributed to burdens. Given that recurrence is associated with 5-year survival, pts were required to have data for survival at a landmark of 5 years post-RC or may have died within 5 years of RC. Patients who died

465 Background: The JAVELIN Bladder 100 clinical trial demonstrated a significant overall survival and progression-free survival benefit with avelumab 1LM + best supportive care (BSC) vs BSC alone for la/mUC not progressing on platinum-based chemotherapy (PBC). PATRIOT-II aims to describe RW data for avelumab 1LM treatment (tx) of patients (pts) with la/mUC. Methods: PATRIOT-II collected data from pts with la/mUC treated in 37 geographically dispersed oncology practices/communities and academic centers in the US. Pts who initiated avelumab 1LM following PBC were retrospectively enrolled and will be followed up via medical record review for 52 weeks post avelumab 1LM initiation. This analysis focused on pt characteristics and tx data from la/mUC diagnosis through the PBC period and at avelumab 1LM initiation. Disease and PBC tx characteristics, as well as response to PBC, were assessed. All analyses were descriptive. Results: A total of 160 pts were enrolled (Table), 118 (74%) were white, non-Hispanic, 16 (10%), were Black, Asian, or Hispanic, and the rest unknown; 102 (64%) were current or former smokers. 77 (48%) were tested for PD-L1 via various assays, with 44 (57%) of those tumor samples reported as positive. 1L PBC was cisplatin-based in 100 (63%) of pts and carboplatin-based in 60 (38%). Pts received a median of 4 PBC cycles (interquartile range [IQR], 3-6) for a median of 13 weeks (IQR, 10-17). 31 (19%) discontinued PBC due to unacceptable side effects/toxicity. Best observed response was complete response in 21 (13%), partial response in 109 (68%), and stable disease in 17 (11%), with the remainder unknown. Median time to first imaging was 10 weeks (IQR, 5-14) after PBC initiation. 23 (14%) were hospitalized while receiving PBC, and 25 (16%) were seen in the emergency department. Pts proceeded to avelumab 1LM at a median of 4 weeks (IQR, 3-6) following PBC completion. Avelumab was administered at 800 mg every 2 weeks in 130 (81%), 10 mg/kg in 15 (9%), 800 mg in 7 (4%) pts. Conclusions: This ‘RW’ study offers valuable insights into characteristics and outcomes of pts with la/mUC treated in the US. Baseline factors, tx patterns and response to PBC were consistent with usual therapy paradigms in the 1L induction setting. Ongoing trials are evaluating the optimal number of PBC cycles and predictive biomarkers. Limitations include the retrospective nature, lack of randomization and central review, potential selection and confounding biases. [Table: see text]

488 Background: Elective nodal irradiation for patients with muscle-invasive bladder cancer (MIBC) undergoing trimodal therapy (TMT) is controversial. In patients with node-negative (N0) MIBC, the benefit of elective whole-pelvis concurrent chemoradiotherapy (WP-CCRT) compared to bladder-only (BO)-CCRT has not been demonstrated. Currently, the National Comprehensive Cancer Network (NCCN) guidelines do not recommend whether to include pelvic nodes in the radiation field. Using real-world data from the National Cancer Database (NCDB), we sought to compare the overall survival (OS) between BO-CCRT and WP-CCRT for MIBC. Methods: Using the 2019 NCDB Participant User File, we identified cases of MIBC diagnosed between 2017 and 2018. We selected patients with clinical T2-T4N0M0 disease receiving TMT as first-line treatment. TMT was defined as transurethral resection of bladder tumor followed by CCRT: 60–65 Gy of RT delivered to the bladder with concurrent single- or multiple-agent chemotherapy. Patients were stratified into BO-CCRT vs. WP-CCRT. Overall survival (OS) analysis was performed using Kaplan-Meier estimates and multivariable Cox proportional hazards regression analysis. The variables included in the multivariable Cox regression model were age, sex, race, comorbidity burden (as per the Charlson-Deyo comorbidity index), facility type, insurance status, median income quartile, rurality, distance from facility, and clinical T stage. Results: A total of 605 patients receiving TMT for MIBC were identified: 162 (26.8%) BO-CCRT and 443 (73.2%) WP-CCRT. The median follow-up time was 25.6 months (interquartile range [IQR]: 4.8-42.6) and 28.7 months (IQR: 3.0-51.6) for BO-CCRT and WP-CCRT, respectively. The median OS was 32.9 months (95% confidence interval [CI] 30.8 – not reached) and 48.3 months (95% CI 39.6 – not reached) for BO-CCRT and WP-CCRT, respectively. However, multivariable Cox regression analysis failed to find an association between WP-CCRT (hazard ratio [HR] 1.08, 95% CI 0.76-1.54) and improved OS, compared to BO-CCRT. Conclusions: Elective nodal-irradiation (WP-CCRT) in the setting of TMT for MIBC was not associated with a benefit in OS compared to BO-CCRT.

10 Background: Penile carcinoma (PeCa) is a rare malignancy with a mean age at diagnosis of 60 years. PeCa is epidemiologically associated with phimosis, HPV, HIV, tobacco, obesity, Psoralen and ultraviolet A photochemotherapy and lichen sclerosis. However, the prevalence and type of pathogenic germline variants (PGVs) associated with PeCa are unknown. Methods: A retrospective cohort of patients (pts) with PeCa who underwent germline testing (range of genes tested, 1-134) from 10/2016 to 5/2022 at a large commercial laboratory (Invitae) was evaluated. Clinician-reported clinical and demographic information from test requisition forms (TRF) were analyzed and the frequency and type of PGVs was determined. Pts were identified via keywords and/or ICD-10 codes for PeCa, but the final study cohort was limited to those whose diagnosis could be corroborated by details in the TRF and/or accompanying medical records. Pts with other pathologies were excluded. Results: Of the 29 pts who met inclusion criteria, the majority were White (65.5%), with a median age (range) of 62.5 years (36-79) at diagnosis. 44.8% of pts had documented squamous cell carcinoma (SCC) pathology, 55.2% of pts had an additional non-PeCa cancer, and 62.1% of pts had a documented family history of relevant cancers (penile, prostate, breast, ovarian, pancreatic and/or colorectal). Among 29 pts with PeCa, 3 harbored PGVs (10.3%) and 16 (55.2%) had > 1 variants of uncertain significance (VUS) in the absence of a PGV. Of the 3 positive pts, 2 harbored BRCA2 PGVs and one harbored a RAD51C PGV. One pt with a BRCA2 PGV had additional malignancies of the prostate and pancreas. Conclusions: This is the first study to our knowledge reporting PGVs in PeCa. PGVs in DNA repair genes ( BRCA2, RAD51C) were identified in 10.3% of selected high-risk PeCa pts with the majority exhibiting other malignancies or family history of malignancies. Larger cohorts of PeCa patients should be studied in pts with different ethnicities. Nonetheless, these data highlight the potential role of germline testing in selected PeCa pts as a tool to aid in clinical management, cascade testing and potential therapeutic relevance in the future.

540 Background: Determining a benefit from ICIs radiographically may take months and may be confounded by pseudoprogression. The NLR & RDW are readily accessible inflammatory markers from routine peripheral blood analysis and have been associated with outcomes in malignancies. We evaluated the association of early changes in NLR and RDW within 4 weeks after initiating ICI with any regression of tumor (ART) and overall survival (OS) in mUC. Methods: This study included de-identified data from Dana-Farber Cancer Institute in pts with mUC who were treated with ICIs from 2015 to 2020. Age, gender, setting (untreated vs. post-platinum), sites of metastasis (mets), performance status (PS), platelet count, RDW, and NLR at baseline and 3-4 weeks after initiating the ICI were collected. The primary objective was to assess the association of early increase in NLR by ≥1.0 from baseline or RDW at 3-4 weeks (as a continuous variable) post-ICI therapy with ART and OS. ART was assessed via subsequent imaging at any time point while on ICI. A multivariable logistic regression model and Cox proportional-hazards model were employed to identify the association of NLR changes with ART and OS, respectively, using backward selection. Results: A total of 330 pts were evaluable. The median age was 70 years, 72.1% (n = 298) were male and 69.4% (n= 227) received post-platinum ICI (remaining were platinum naïve). 46.5% (n = 146) experienced ART and the median OS was 13 months (11.14-16.14). An increase in NLR ≥ 1 in 3-4 weeks was associated with a lower rate of ART (OR: 0.41, 95% CI 0.24-0.70; p: 0.001) and worse OS (hazard ratio [HR]: 1.84, 95% CI 1.37-2.46; p < 0.0001) on multivariable analysis (Table). Higher RDW values at 3-4 weeks were associated with worse OS (HR: 1.08, 95% CI 1.03-1.14; p: 0.0004) but were not associated with ART. Conclusions: In pts with mUC initiating ICI, an early increase in NLR ≥ 1 and higher RDW in 3-4 weeks were associated with poor outcomes. Early changes in these readily available variables may enable early modification or intensification of therapy to improve outcomes. External validation of these findings is warranted. [Table: see text]

467 Background: Neuroendocrine, small cell, or large cell carcinoma originating from the urothelium (uro-NE/SCC/LCC) is rare. Outcomes for metastatic disease are dismal. Treatment is extrapolated from small cell lung cancer, for which immune checkpoint inhibitors (ICIs) have modest activity. Preliminary activity has been reported with ICI for uro-NE. We aimed to compare real-world progression-free survival (PFS) and overall survival (OS) between ICI-containing and non-ICI-containing regimens in the first line (1L) metastatic setting for uro-NE/SCC/LCC. Methods: We performed a retrospective study at 11 cancer centers. Patients (pts) who received systemic therapy (2011-2021) for biopsy confirmed metastatic uro-NE/SCC/LCC were included. Pts with metastasis within 6 months of (neo)adjuvant chemotherapy (CT) (n=16) were excluded from 1L analyses. Results: 102 pts with metastatic uro-NE/SCC/LCC were evaluable. 17 (16.7%) had NE histology, 81 (79.4%) SCC, and 4 (3.9%) LCC. NE/SCC/LCC was mixed with urothelial histology in 19 (18.6%). Primary tumors were most often in the bladder (84.3%, n=86), less frequently upper tract (11.8%, n=12) or urethra (3.9%, n=4). 42 pts (41.2%) were previously treated for localized disease, the rest were de novo metastatic (n=60, 58.8%). Pts who received an ICI in any line (n=61) had significantly longer OS (p=0.038) than pts that never received an ICI (n=41). As shown in the table, in the 1L, ICI-containing regimens (n=33) resulted in significantly longer PFS, but not OS or ORR compared to non-ICI regimens (n=53). Subdividing 1L regimens into ICI without CT (n=14), CT without ICI (n=53), or ICI + CT (n=19), both PFS and OS were significantly different with similar ORR. ICI w/o CT had the longest median PFS and OS with an ORR 57.1% comparable to CT regimens. Of 61 pts that received ICI in any line, 14 (23.0%) had an immune-related adverse event of any grade; 11 (18.0%) received steroids. Conclusions: This is the largest ever report of ICI for metastatic uro-NE/SCC/LCC. ICIs were associated with improved outcomes with expected added toxicity. Further prospective investigation of ICI regimens is warranted. [Table: see text]

477 Background: First-line therapy for metastatic urothelial carcinoma of the bladder (mUC) consists of platinum-based chemotherapy in most patients and PD1/L1 inhibitors in selected patients. Multiple combination chemo-immunotherapy trials failed to show a clear benefit over chemotherapy alone. We sought to use real-world data to evaluate clinical and sociodemographic factors associated with receipt of first-line chemotherapy, immunotherapy or combination chemo-immunotherapy treatment for metastatic bladder cancer and examined differences in overall survival (OS). Methods: We used the National Cancer Database to identify patients with stage IV UCB diagnosed between 2014 and 2018, who were treated with first-line immunotherapy, chemotherapy, or combination treatment. We performed multivariable logistic regression modeling to determine factors associated with treatment receipt. An extension of inverse probability treatment weighting (IPTW) obtained from multinomial logistic regression was used to balance clinical and sociodemographic differences between treatment groups. Adjusted Kaplan-Meier survival analysis and multivariable Cox proportional hazards regression were used to evaluate the association between treatment and OS. Results: A total of 4,169 patients were identified in the cohort; 3,255 (78.1%) were treated with chemotherapy, 601 (14.4%) with immunotherapy, and 313 (7.5%) with combination treatment. Multivariable analysis identified increasing age (RRR: 1.07, 95% CI, 1.06-1.08), comorbidity burden (Charlson-Deyo 2, RRR: 1.65, 95% CI, 1.21-2.24 and Charlson-Deyo 3, RRR: 2.11; 95% CI, 1.51-2.93), and treatment at an academic facility (RRR: 1.26; 95% CI, 1.03-1.53) as independent predictors of receiving immunotherapy. Treatment at an academic facility (RRR: 1.29, 95% CI, 1.01-1.65) was associated with receipt of combination treatment. After IPTW, we found that combination therapy (hazard ratio [HR]: 0.72; 95% CI, 0.62-0.83), but not immunotherapy alone, was associated with improved survival compared to chemotherapy. These data are limited by inability to determine platinum eligibility, and residual confounding. Conclusions: Patients with older age and more comorbidities were more likely to receive immunotherapy than chemotherapy for first-line treatment of metastatic urothelial carcinoma of the bladder. Modest real-world utilization of chemo-immunotherapy was observed to be higher in academic centers and was associated with improved survival compared to chemotherapy. The study is limited by retrospective design; prospective data are necessary to identify patients who may benefit from combination chemo-immunotherapy.

559 Background: BLASST-1 is multi-center phase II trial evaluating neoadjuvant nivolumab (N) with gemcitabine-cisplatin (GC) for patients (pts) with MIBC undergoing radical cystectomy (RC) (NCT03294304). 41 pts with MIBC (cT2-T4a, N≤1, M0) were enrolled between Feb 2018 and June 2019; (cT2N0 90%, cT3N0 7%, cT4N1 3%). Pts received C (70mg/m2) IV on D1, G (1000mg/m2) on D1, D8 and N (360 mg) IV on D8 every 21 days for 4 cycles followed by RC within 8 wks. Primary endpoint was pathologic down staging (PaR; ≤pT1N0). Safety, Relapse-free survival (RFS), Progression-free survival (PFS) and biomarker analyses were secondary endpoints. PaR rate was 65.8%, pCR (≤pT is N0) rate was 49% and there were no safety concerns or delays to RC. At a median follow-up of 15.8 mos, 12-month RFS rate was 85.4% and PFS including death from any cause was 83%. We now report correlation of PaR with tumor mutation patterns of responders (R) and non-responders (NR) using Whole Genome Sequencing (WGS). Methods: DNA was extracted from pre-treatment tumor samples and sequenced to an average depth of 150X and DNA extracted from matched normal tissue (peripheral blood) to a mean depth of 50X. We analyzed 32 Tumor/Normal pairs and 6 Tumor only Whole Genome Samples; 26 pts were classified as (R) and 12 as (NR). Raw sequencing data samples were aligned to hg38 genome build using Burrows-Wheeler Aligner (BWA) followed by duplicate-read removal and base-quality score recalibration using the Genome Analysis Toolkit (GATK). Somatic SNV and INDELS were called by combination of 5 callers (Mutect2, Strelka, VarScan, Platypus and SomaticSniper) for Tumor/Normal pairs and Mutect2 for Tumor only samples following the guidelines of GDC DNA-Seq analysis pipeline. Set of genes known to be significantly mutated in MIBC and shown to impact response/resistance to chemotherapy/immunotherapy respectively were selected. Samples were grouped by response status. Results: Median tumor mutational burden (TMB) for the dataset closely matches with TCGA results. Genes ERCC2, ARID1A, DSP, HMCN1, ERBB2, ERBB3, STAG2, BRCA2 present in (R) only, whereas VHL, ERCC4, PALB2, CDKN2A and CSMD3 present in (NR) only. We also grouped genes based on their biological processes by known Oncogenic Signaling Pathways and the 3 most common pathways are Genome Integrity, RTK Signaling and Transcription Factor with the latter two primarily enriched in (R). We identified a SNP rs2853669 in 5 (NR) and 14 (R). Conclusions: The genomic analysis suggests ERCC2, ARID1A, DSP, HMCN1, ERBB2, ERBB3,STAG2, BRCA2 correlated with PaR and VHL, ERCC4, PALB2, CDKN2A and CSMD3 correlated with lack of response. In addition, RTK Signaling and Transcription Factor were primarily enriched in (R). This genomic correlation of response/resistance to neoadjuvant chemo-immunotherapy in MIBC can help guide future biomarker-driven studies. Clinical trial information: NCT03294304 .

531 Background: Neoadjuvant cisplatin-based chemotherapy (NAC) is established in the management of MIBC. Pathologic complete response (pCR, ypT0N0) and downstaging (

5 Background: Management options for patients (pts) with advanced (locally advanced or metastatic) PeCa are limited. The GSRGT assembled an international cohort of pts with advanced PeCa treated with ICI to evaluate toxicity and clinical outcomes. Methods: We retrospectively collected data on pts with advanced PeCa receiving ≥1 cycle of ICI between 2015-2022 at 18 medical centers in the US, Europe, and Asia. Immune-related adverse events (irAE) were graded per the Common Terminology Criteria for Adverse Events v5.0. Overall survival (OS) and progression-free survival (PFS) were estimated by the Kaplan-Meier method. Objective response rate (ORR) was determined by the clinical investigator per RECIST 1.1 criteria, whenever feasible. Results: Among 72 pts with advanced PeCa treated with ICI, 24 (33%) were Hispanic and 7 (10%) were Black. 60 (83%) pts had metastases while the remainder had locally advanced disease. The median age was 64 (inter-quartile range (IQR): 54,70) years and 48 (67%) had ECOG performance status ≥1. Most pts (n=60, 83%) were treated in the ≥2nd line setting and received pembrolizumab (n=23), nivolumab (n=15), cemiplimab (n=15), nivolumab and ipilimumab (n=7), or other anti-PD1/L1-based therapies (n=12). Among 37 pts with available data on HPV status, 24 (65%) were HPV+. 3 (4%) pts were HIV+. irAE of any grade occurred in 18 (25%) pts, 7 (10%) were grade ≥3, 7 (10%) required steroids, 6 (9%) required hospitalization, and 8 (11%) led to treatment discontinuation. The median OS and 24-month OS and median PFS and 24-month PFS were 9.4 (95%CI: 6.8, 12.8) months and 19.3% (95%CI: 9.2, 32.1) and 2.8 (95%CI: 2.1, 3.9) months and 11.2 % (95%CI: 4.9, 20.2), respectively. Among 66 pts evaluable for response, ORR was 7/66 (11%) (2 with complete response, 5 with partial response), and 16 (24%) pts had stable disease for a disease control rate of 35%. The median duration of response was 7.9 (IQR: 3, not reached) months. Conclusions: In the largest retrospective cohort of ICI-treated advanced PeCa, ICI showed no new safety signals, however, overall anti-tumor activity was limited. Future translational studies are needed to identify pts that are more likely to derive clinical benefit from ICI.

We aim to describe reporting and representation of minority patient populations in immune checkpoint inhibitor (ICI) clinical trials and assess predictors of enrollment disparity.Trial-level data were acquired from eligible phase II and III trials. Population-based estimates were acquired from the SEER 18 and Global Burden of Disease incidence databases. Trials reporting race, age, and sex were summarized using descriptive statistics. Enrollment-incidence ratio (EIR) was used to assess representation of subgroups. Average annual percentage change (AAPC) in EIR was calculated using Joinpoint Regression Analysis. Trial-level characteristics associated with EIR were assessed using multivariable linear regression.A total of 107 trials with 48,095 patients were identified. Participation of Black, White, Asian, Native American, Pacific Islander, and Hispanic participants was reported in 65 (61%), 77 (72%), 68 (64%), 40 (37%,) and 24 trials (22%), respectively. Subgroup analyses of clinical outcomes by race, age, and sex were reported in 17 (22%), 62 (78%), and 57 (57%) trials, respectively. Women (trial proportion [TP]: 32%; EIR: 0.90 [95% confidence interval [CI]: 0.84-0.96]), patients aged ≥65 years (TP: 42%; EIR: 0.78 [95% CI: 0.72-0.84]), Black participants (TP: 1.9%; EIR: 0.17 [95% CI: 0.13-0.22]) and Hispanics (TP: 5.9%; EIR: 0.67 [95% CI: 0.53-0.82]) were underrepresented. Representation of Black patients decreased significantly from 2009 to 2020 (AAPC: -23.13). Black participants were significantly underrepresented in phase III trials (P.001).The reporting of participation by racial or ethnic subgroup categories is inadequate. Women, older adults, as well as Black and Hispanic participants are significantly underrepresented in ICI clinical trials.

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in Journal of Clinical Oncology, to patients seen in their own clinical practice.

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.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.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 was40% 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).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 rate30 mL/min and significant comorbidities.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.

Prior durvalumab (anti-PD-L1 agent) studies in platinum-refractory metastatic urothelial carcinoma evaluated a dose of 10 mg/kg administered every two weeks. The nonrandomised phase 3b STRONG study (NCT03084471) evaluated the safety and efficacy of fixed-dose durvalumab at a more convenient dosing schedule in a previously treated patient population, more similar to a real-world clinical setting.867 patients with urothelial or nonurothelial urinary tract carcinoma (UTC) who progressed on or after platinum or nonplatinum chemotherapy were treated with durvalumab 1500 mg every four weeks; 87% had an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-1, and 13% had an ECOG PS of 2. The primary end-point was the incidence of adverse events of special interest (AESIs), including immune-mediated AEs (imAEs). Secondary and exploratory end-points included overall survival (OS), objective response rate (ORR) and disease control rate (at six and 12 months) (DCR).AESIs of any grade were reported in 51% of patients (8% grade ≥ 3). The incidence of imAEs was 11% (2% grade ≥ 3). The median OS was 7.0 months (95% confidence interval [CI]: 6.4-8.2) and ORR was 18% (95% CI: 14.8-20.6), with complete responses in 5% of patients and a DCR at six months of 19% (95% CI: 16.1-22.1).Fixed-dose durvalumab monotherapy every four weeks has an acceptable safety profile and yields durable clinical activity in previously chemotherapy-treated patients with UTC. Safety and efficacy are consistent with previous durvalumab studies and other anti-PD-1/PD-L1 agents in this setting. CLINICALTRIALS.NCT03084471https://clinicaltrials.gov/ct2/show/NCT03084471.

2622 Background: We previously showed that CDKN2A genomic alterations (GAs) are associated with resistance to ICI (Adib E, Clinical Cancer Research, 2021). The majority of such GAs are homozygous deletions, which commonly (̃50-80%) include MTAP, located 100kb telomeric of CDKN2A. MTAP loss leads to 5′-deoxy-5′-methylthioadenosine (MTA) accumulation and immunosuppressive effects in tumors. We examined combined CDKN2A/MTAP deletion vs. CDKN2A deletion/mutation alone as predictors of poor ICI response. Methods: We curated clinical data for cancer patients (pts) treated with ICI at Dana-Farber Cancer Institute through 6/2021, who had targeted panel sequencing. Inclusion criteria were: ICI in metastatic setting, ≥2 cycles, no concurrent systemic therapy, cancer type with > 50 pts treated. CDKN2A/ MTAP GAs were defined as a deep deletion affecting both genes; CDKN2A only GAs included both homozygous deletions and truncating mutations. Hazard ratios (HR) for overall survival (OS) and time-to-treatment failure (TTF) were derived using multivariable Cox regression, adjusted for prior lines of therapy, treatment type (single vs. combination ICI), tumor mutational burden and ECOG PS. We also used a machine learning approach to quantify the density of tumor-infiltrating lymphocytes (TILs) in digital whole-slide H&E images of 144 melanoma pts with available genomic data. Results: 921 pts with 6 cancer types were studied: non-small cell lung cancer (NSCLC, n = 366), melanoma (mel, n = 228), urothelial carcinoma (UC, n = 120), esophagogastric carcinoma (EGC,n = 90), head and neck squamous cell carcinoma (HNSCC, n = 58), and renal cell carcinoma (RCC, n = 59). UC pts with MTAP/ CDKN2A GAs had shorter OS and TTF than pts without GA in either gene (OS HR = 1.9[1.1-3.4], p = 0.005; TTF HR = 1.8[1.0-3.1], p = 0.0016) after adjusting for covariates. Similar results were seen for melanoma (OS HR = 2.5[1.4-2.6],p = 0.00065; TTF HR = 1.9[1.1-3.2],p = 0.018). There was no significant difference between pts with CDKN2A GA only and those without GA in either gene for OS or TTF in either UC or melanoma. CDKN2A/MTAP status was not associated with significantly shorter survival for NSCLC and EGC; while the analysis was confounded by HPV events for HNSCC, and underpowered for RCC. ML-based analysis of digital slides for melanoma, showed that tumors with CDKN2A GAs only (n = 42) had similar median density of TILs compared to tumors without GAs in either gene (n = 84; 920 vs. 943 TILs/mm2; p = 0.42). In contrast, tumors with co-occurring CDKN2A/ MTAP GAs had lower TIL density (529 TIL/mm2, n = 17 vs. 925 TIL/mm2, n = 126 (pooled); p = 0.018, Wilcoxon rank sum). Conclusions: In this study, we showed that co-occurrence of MTAP/CDKN2A GAs, but not CDKN2A GA only, was associated with worse outcomes in pts with UC and melanoma treated with ICI. Lower TIL density was also seen in melanoma tissue samples with combined MTAP/CDKN2A GA.

e16550 Background: Improved computational power and modern algorithms have generated significant interest in radiomics for cancer diagnosis and staging. Here we assess the performance of deep learning (DL) models as a means for feature extraction in combination with supervised machine learning (ML) algorithms for accurate staging and chemotherapy response assessment of bladder cancer. Methods: Deidentified grayscale CT images from bladder cancer patients scheduled to undergo radical cystectomy were included in this retrospective study. These images were manually annotated with two regional masks (normal region and cancer region). Five DL models- namely, AlexNet, GoogleNet, InceptionV3, ResNet-50, and XceptionNet pre-trained on the ImageNet dataset, a public dataset, were then fine-tuned on our bladder CT scan data to extract features. Through feature selection process, the subset of the features was used to build ML classifiers for classification. The classification was performed using five different ML classifiers, namely k-Nearest Neighbor (KNN), Naïve-Bayes (NB), Support Vector Machine (SVM), Linear Discriminant Analysis (LDA), and Decision Tree (DT). The classification task was performed with 10-fold cross-validation, and each of the experiments contained a different but not mutually exclusive subset of samples. The evaluation metrics include accuracy, sensitivity, specificity, precision, and F1-score. Results: A total of 200 deidentified grayscale CT images of 100 patients with histologically proven bladder cancer, were included in this study. For experiment (1) normal vs. cancer, the LDA classifier on XceptionNet based features provides the best performance with an accuracy of 86.07%, sensitivity of 96.75%, specificity of 69.65%, precision of 83.07%, and F1-score of 89.39%. For experiment (2) non-muscle invasive Cancer (NMIBC) vs. muscle invasive bladder cancer (MIBC), the LDA classifier on XceptionNet based features provided the best performance with an accuracy of 79.72%, sensitivity of 66.62%, specificity of 87.39%, precision of 75.58%, and F1-score of 70.81%. For experiment (3) T0 lesion vs. MIBC, the LDA classifier on XceptionNet based features provides the best performance with an accuracy of 74.96%, sensitivity of 80.51%, specificity of 70.22%, precision of 69.78%, and F1-score of 74.73%. Conclusions: Our proposed model has shown good results in differentiating normal vs cancer and promising performance in differentiating T0 vs MIBC after chemotherapy treatment. We are expanding our dataset to further improve the performance in differentiating T0 vs MIBC. In addition, we will investigate the applicability of GAN for data augmentation to address data limit. We believe the hybrid DL and ML framework may facilitates radiologists' decisions and clinical decision-making in patients with bladder cancer.

4565 Background: Advanced urothelial carcinoma (aUC) has a poor long-term prognosis. Despite new clinical trial data for novel therapies including PD-1/L1 inhibitors, data on real-world (RW) treatment patterns and overall survival (OS) in aUC patients (pts) treated with first line (1L) therapy are limited. Methods: This retrospective observational study describes the contemporary RW 1L treatment patterns and OS in aUC pts stratified by cisplatin (cis)-eligibility (based on accepted criteria) and treatment. Data were from the nationwide Flatiron Health longitudinal electronic health record-derived database, comprising de-identified patient-level structured and unstructured data. Eligible pts were adults diagnosed with aUC from May 2016-Oct 2020 and followed until death or end of data availability in July 2021. OS was estimated using Kaplan-Meier methods and compared via multivariable Cox proportional-hazard models adjusted for clinical covariates. Results: Of 4,300 aUC diagnosed pts, 3,311 (77.0%) received 1L treatment; 1836 (55.5%) cis-ineligible, 1475 (44.5%) cis-eligible. Differences between cis-ineligible and cis-eligible pts were observed, with cis-ineligible more likely to be older (mean age, 75.0 vs 69.0 yrs), have lower CrCl (median, 45.3 vs 80.7 mL/min), and worse ECOG-PS (2+, 29.2 vs 0%). Only 44.4% received 2L therapy: 38.3% cis-ineligible vs 52.0% cis-eligible. Median OS in all 1L treated pts was 11.0 (95% CI, 10.3 – 11.5) mo and was shorter in cis-ineligible than cis-eligible pts (8.6 [95% CI, 8.1 – 9.2] vs 14.4 [95% CI, 13.4 – 16.4]; hazard ratio [HR], 0.8 [0.7 – 1.0]). A number of cis-ineligible pts received cis, and many cis-eligible pts did not (Table), suggesting physicians consider clinical factors beyond conventional criteria to determine cis-eligibility. Cis + gemcitabine (gem) or MVAC was associated with longer OS vs other treatments regardless of cis-eligibility (Table). Conclusions: Clinical outcomes in 1L aUC pts were poor, particularly for cis-ineligible pts, which may be partly driven by the specific regimen administered. Many aUC pts did not receive 1L treatment and among those who did, less than half received 2L therapy. These data highlight the need for more effective and tolerable 1L therapy for all aUC pts. [Table: see text]

TPS4611 Background: The utilization of neoadjuvant immune checkpoint inhibitor (ICI) therapy, including anti-PD1/L1 agents, prior to radical cystectomy (RC), is an emerging paradigm in muscle invasive bladder cancer (MIBC). Pathologic complete responses (pCR) have been observed in 25-40% of patients with neoadjuvant PD1/L1 inhibitor monotherapy for cisplatin-ineligible MIBC. In situ vaccination using stereotactic body radiation therapy (SBRT) may augment T-cell responses to tumor-specific antigens through immunogenic cell death. Sasanlimab (PF-06801591) is a humanized IgG monoclonal antibody that targets PD-1 selectively, for which there are both Phase 1 data and ongoing Phase 3 trials in early-stage urothelial carcinoma. There exists a strong rationale to evaluate a novel strategy of combination neoadjuvant ICI therapy with SBRT as an in situ vaccine to improve loco-regional control and decrease the risk of distant recurrence in cisplatin-ineligible patients with MIBC. Methods: This is a prospective, investigator-initiated, single-arm, single-institution, phase II trial that evaluates neoadjuvant sasanlimab in combination with SBRT as neoadjuvant therapy for patients with MIBC before RC. Eligibility requires patients to be cisplatin-ineligible (one of the following: ECOG-PS=2, creatinine clearance

2649 Background: PLWH and ca are inadequately represented in clinical trials evaluating ICI especially in the setting of low CD4 counts (ct) and elevated HIV viral loads (VL). We assembled an international cohort of PLWH and ca treated with ICI to evaluate toxicity profiles and clinical outcomes. Methods: We retrospectively collected data on 204 PLWH and ca receiving ≥ 1 cycle of ICI between 2015-2021 at 14 academic medical centers in the US and Europe. Immune-related adverse events (irAEs) were graded per the Common Terminology Criteria for Adverse Events (CTCAE) V5.0. Baseline CD4 ct, CD8 ct and HIV VL were collected within 3 months (mo) of ICI initiation when available. Fisher’s exact test was performed to compare categorical variables. Median (med) Overall Survival (OS) and Objective Response Rate (ORR) were calculated for 186 pts treated in the metastatic (met) setting. Results: Among 204 PLWH treated with ICI, 174 (85%) were cis-gender males. 61 (31%) were Black and 34 (18%) were Hispanic/Latinx. Pts were treated with pembrolizumab (n=93), nivolumab (n=71), atezolizumab (n= 20), nivolumab and ipilimumab (n=13), durvalumab (n=6), or avelumab (n=1). Med number of prior lines of systemic therapy was 1 (range: 0-5). Among pts with available baseline data, 36/133 (27%) had CD4 ct

4516 Background: Enfortumab vedotin (EV), an antibody-drug conjugate directed against Nectin-4, demonstrated longer overall survival (OS) and progression-free survival (PFS) in the confirmatory phase 3, randomized, open-label EV-301 trial at the prespecified interim analysis. The longer-term clinical profile of EV is unknown. Data from 12 additional months of follow-up in EV-301 are presented. Methods: In EV-301 (NCT03474107), patients with locally advanced or metastatic urothelial carcinoma (la/mUC) who had received a prior platinum-containing chemotherapy and had disease progression during or after PD-1/L1 inhibitor treatment were randomized 1:1 to receive either EV 1.25 mg/kg on Days 1, 8, and 15 of each 28-day cycle or investigator-chosen standard chemotherapy with docetaxel, paclitaxel, or vinflunine. The primary endpoint was OS; secondary endpoints included investigator-assessed PFS per RECIST v1.1, as well as safety and tolerability. Efficacy and safety findings from July 30, 2021, approximately 1 year after the interim analysis (July 15, 2020), are reported. Results: Overall, 608 patients with la/mUC were randomly assigned to EV (n = 301) or chemotherapy (n = 307). As of July 30, 2021, 444 deaths had occurred (EV, n = 207; chemotherapy, n = 237). After a 23.75-month follow-up, median OS was significantly prolonged by 3.97 months with EV compared with chemotherapy (median OS: 12.91 vs 8.94 months, respectively; HR = 0.704 [95% CI: 0.581-0.852], 1-sided P= 0.00015). Additionally, the OS benefit of EV was retained in the majority of prespecified subgroups. PFS also was improved with EV (median 5.55 months) vs chemotherapy (median 3.71 months) (HR = 0.632 [95% CI: 0.525-0.762]; 1-sided P< 0.00001). Rates of treatment-related adverse events (TRAEs; 93.9% vs 91.8%), including serious TRAEs (22.6% vs 23.4%), were comparable between the EV and chemotherapy groups. Rates of grade ≥3 TRAEs were ̃50% in both groups. Conclusions: EV continues to show significant and consistent survival advantage over standard chemotherapy in patients with treatment-experienced la/mUC. No new safety signals were identified. With robust clinical benefit and a tolerable safety profile, EV maintains its place as a standard of care for this aggressive disease. Clinical trial information: NCT03474107.

4569 Background: Prior studies of the UC germline landscape centered around White patients with minimal representation of other racial populations. Herein, we examine the frequency of germline pathogenic and likely pathogenic (P/LP) variants in 2,582 patients with UC from various racial populations. Methods: 2,582 patients with UC underwent germline testing of 1 to 126 genes using massively parallel sequencing with customized capture bait-sets to analyze exonic regions, flanking intronic regions, and copy number alterations (CNAs). P/LP variants including single nucleotide variants, indels and CNAs were reported. Fisher’s Exact test and multivariable logistic regression were used after accounting for the number of genes tested, age at diagnosis, site of disease (upper versus lower tract), gender, family history of UC, and personal history of any cancer. Results: Among the 2,582 patients with UC, median age at diagnosis was 63 years (range, 4-90) and 1158 (44.8%) were female. There were 58 Asians (2.2%), 110 Blacks (4.3%), and 2,414 Whites (93.5%). Overall, 1,639/2,582 (63.5%) patients had a personal history of another cancer and 284/2,393 (11.9%) had history of UC in a family member. 465 P/LP variants were identified in 18% of patients, among whom 286 (11.1%) harbored ≥1 clinically actionable variants. P/LP in cancer-associated genes were most frequently reported in MSH2 (72/2,512, 2.9%), monoallelic MUTYH (45/2,136, 2.1%), BRCA2 (44/2,299, 1.9%) and MSH6 (47/2,511, 1.9%). Patients with upper tract UC had significantly more P/LP (72/247, 29.1%) compared to lower tract UC (332/2,076, 16%, p= 1.3x10-5). Age at diagnosis, gender, personal history of other primary cancers, or family history of UC were not significantly associated with the prevalence of P/LP variants. There were no significant differences ( p= 0.33) in P/LP variants across Asians (11/58, 19.0%), Blacks (14/110, 12.7%), and Whites (440/2,414, 18.2%) although a trend towards lower P/LP in Blacks is notable. Compared to Whites, Blacks and Asians harbored significantly more variants of unknown significance (VUS, Whites vs Blacks: 241/2414 vs 25/110, p= 0.0015; Whites vs Asians: 241/2414 vs 17/58, p= 4e-7). Asians with UC harbored significantly more P/LP variants in ATM (2/50, 4%) compared to Whites (30/2122, 1.4%, OR = 1.1 [95% CI, 1.0-1.2]) and Asian controls from the gnomAD Database. There were no significant differences across racial populations for other highly altered genes ( BRCA1/2, CHEK2, FH, MSH2/6, MUTYH) or for actionable variants. Conclusions: Germline P/LP variants were identified in 18% of patients with UC and were enriched in upper tract tumors. Although no significant differences in P/LP prevalence were noted among patients of different racial populations, a trend towards lower P/LP in Blacks and a higher rate of VUS in Asians and Blacks suggest that ongoing analysis by genetic ancestry may provide richer admixture data and insights.

485 Background: The renin-angiotensin system (RAS) has been demonstrated to modulate cell proliferation, desmoplasia, angiogenesis and immunosuppression. Angiotensin pathway inhibitors are postulated to favorably reprogram the stroma in part by inhibition of transforming growth factor-β, a major mechanism of resistance, and have been previously reported to be associated with improved outcomes in the setting of immune checkpoint inhibitors (ICIs) for metastatic urothelial carcinoma (Jain R, Clin Genitourin Cancer 2021). In this analysis, we examined the association of angiotensin inhibitors in the setting of NAC for MIBC preceding radical cystectomy (RC). Methods: Pts with MIBC who received NAC preceding radical cystectomy were assembled from 3 institutions: Dana-Farber Cancer Institute (DFCI), Moffitt Cancer Center (MCC) and McGill University Health Center (MUHC). Pts were retrospectively assessed for the association of concurrent ACEi/angiotensin receptor blockers (ARB) use at initiation of NAC on pathologic complete response (pCR), defined as pT0N0, and overall survival (OS). Pathologic features, performance status (PS), clinical stage, type/number of cycles of NAC, and toxicities were collected. The Kaplan-Meier method was used to estimate OS. Logistic and Cox regression were used to explore factors potentially prognostic for pCR and OS respectively. Results: 302 MIBC pts who received NAC preceding RC were available from 3 institutions: DFCI (n = 187), MCC (n = 50) and MUHC (n = 65). Overall, 141 pts (46.7%) received Cisplatin/Gemcitabine, 130 (43.1%) received dose dense MVAC and the remaining received other regimens. The overall pCR rate was 26.2%. The 5-year OS was 62%. 63 (20.9%) pts were receiving an ACEi and 41 (13.6%) were receiving an ARB. ACEi prior to NAC approached significance for association with pCR (odds ratio = 1.71 (95% CI = 0.94-3.11) p = 0.077). Pts with cT3/4N0-N1 disease receiving ACEi had higher pCR rates (30.8% (8/26) vs 17.7% (14/98), p = 0.056) than those not on ACEi; no difference was observed for pts with cT2N0 tumors (31.1% vs 31.3%, p = 0.99). pCR, ECOG-PS and clinical stage were significantly associated with improved OS. ARB intake was not associated with pCR or OS. Conclusions: ACEi intake appeared potentially associated with increased pCR in pts with MIBC receiving NAC, which was more pronounced in those with higher clinical stages cT3/4N0-1. Given the association of pCR with OS, our data suggest the potential relevance of angiotensin as a therapeutic target in aggressive MIBC. Future prospective validation is warranted to repurpose angiotensin inhibitors in this setting, given their excellent toxicity profile and low costs.

511 Background: PD(L)1 inhibitors can achieve durable responses in aUC but only in a minority of patients (pts). Combination strategies with agents that “prime and stimulate” the immune system may improve outcomes. CV301 comprises 2 recombinant poxviruses, Modified Vaccinia Ankara (MVA) and Fowlpox (FPV), encoding the human transgenes for CEA, MUC-1, and a Triad of Co-stimulatory Molecules (TRICOM: ICAM-1, LFA-3, and B7-1). MVA-CV301 is used for priming and FPV-CV301 is used for booster doses. Preliminarily, BN-platform vaccine plus PD-(L)1 inhibitors exhibited synergistic preclinical anti-tumor efficacy and the combination of CV301 and anti-PD-(L)1 agent demonstrated an acceptable safety profile. We hypothesized that this combination would be safe and effective in cisplatin-ineligible or platinum-refractory pts with aUC. Methods: A Phase 2, single-arm multicenter trial was designed to study CV301 + atezo as 1st-line treatment in pts with aUC ineligible for cisplatin-based chemotherapy regardless of PD-L1 status (Cohort 1; C1) and in pts progressing on/after platinum-based chemotherapy (Cohort 2; C2). MVA-CV301 was given subcutaneously (SC) on Days 1 and 22 and FPV-CV301 SC from day 43 every 21 days for 4 doses, then every 6 weeks until 6 months, then every 12 weeks until 2 years. Atezo 1200mg IV was given every 21 days. Primary endpoint: objective response rate (ORR). Secondary endpoints: OS, PFS, response duration, AEs and antigen-specific T-cell responses to CEA and MUC-1 by ELISPOT. Using 1-sided α 2.5%/cohort, a 2-stage design with 14/19 and 13/22 stage 1/2 subjects, respectively, will achieve ≥70% power if the true ORR for C1 is 43% and C2 is 33%. 3 C1 and 2 C2 responders were required in stage 1 to move forward. Results: 43 evaluable pts were enrolled and received therapy: 19 in C1; 24 in C 2. Overall, 9 pts experienced ≥ Grade 3 AEs related to the combination of treatment: 5 in C1, and 4 in C2. In C1, 1 pt had partial response (PR), for ORR 5.3% (90%CI: 0.3, 22.6) and 5 (26.3%, 90%CI: 11.0, 47.6) had stable disease (SD) as best response. In C2, 1pt had CR and 1 had PR, for ORR 8.3% (90%CI: 1.5, 24.0) and 3 (12.5%, 90%CI: 3.5, 29.2) had SD as best response. Median PFS and OS in C1 were 2.0 mo and 13.8 mo, and in C2 1.95 and 8.13 mo, respectively. The trial was halted for futility. Responding pts in C2 exhibited T-cell responses to CEA and pts with SD exhibited responses to MUC-1. Conclusions: CV301 + atezo exhibited an acceptable safety profile but did not demonstrate sufficient efficacy in pts with aUC as 1st-line therapy in cisplatin-ineligible pts or in the platinum-refractory setting. The development of effective vaccines to generate robust and durable responses as single agents and/or combined with anti-PD(L)1 remains an unmet need in aUC. Clinical trial information: NCT03628716.

569 Background: Patients with metastatic genitourinary malignancies with neuroendocrine have limited therapeutic options following platinum therapy. Given encouraging results in initial cohort analysis for small cell urinary tract carcinoma, a cohort of any genitourinary malignancy with neuroendocrine differentiation was added to a multicenter, single arm, multi-cohort phase II trial to evaluate the efficacy of N and I in this setting. (NCT 03333616) Methods: Eligible patients had metastatic or locally advanced genitourinary malignancy with neuroendocrine differentiation with an ECOG performance status of 0-2; they may have received any line of prior therapy excluding prior immunotherapy. Patients underwent baseline biopsy and received treatment with N 3 mg/kg and I 1 mg/kg intravenously every 3 weeks for 4 cycles with continued maintenance of N 480 mg IV every 4 weeks. Imaging was performed at 12 weeks and then every 8 weeks through month 6 and then every 12 weeks thereafter. The primary endpoint was investigator assessed objective response rate (ORR) by RECIST 1.1. Results: A total of 27 patients were enrolled between 06/27/2018 and 06/21/2021, 10 (37%) had urinary tract cancer and 17 (63%) had prostate cancer (19 in expansion cohort, 3 urinary tract and 5 prostate cancer from earlier cohorts). The majority (n=25, 93%) patients received prior systemic therapy. Nine (33%) patients received all 4 doses of N and I during the induction period. Nine (33%) patients (7 of whom received 4 cycles N+I) received N maintenance (median number of cycles 9 (range, 2-37)). Median follow-up was 6.8 (range, 0.9-37.3) months. Objective response was achieved in 8 (30%, 80% CI 18%-44%) patients (Table). Median duration of response was not reached with 4 patients maintaining response >9 months. Median progression-free survival time was 2.6 (95% CI 1.8-6.5) months At time of analysis, 13 (48%) death events were reported due to progressive disease, in which 3 were bladder and 10 were prostate cancer. 8 (30%) patients developed treatment-related grade 3 or higher toxicities; one grade 5 toxicity was deemed treatment-unrelated. Conclusions: In this study we demonstrate N+I resulted in objective responses in patients with genitourinary malignancy with neuroendocrine differentiation. ORR of 50% in small cell carcinoma is bladder cancer is noteworthy and will be evaluated further in ongoing expansion cohort of bladder or upper tract carcinoma with variant histology. Clinical trial information: NCT03333616. [Table: see text]

TPS585 Background: Trilaciclib is an intravenous (IV) CDK4/6 inhibitor that has been shown to help protect hematopoietic stem and progenitor cells from chemotherapy (CT)-induced damage (myeloprotection) via transient cell cycle arrest. Trilaciclib is approved in the US to decrease the incidence of CT-induced myelosuppression (CIM) in adult patients with extensive-stage small cell lung cancer receiving certain treatment regimens. An exploratory phase 2 study (NCT02978716) in patients with triple-negative breast cancer showed improved overall survival (OS) in patients receiving trilaciclib prior to CT vs CT alone, regardless of PD-L1 expression. The aim of this exploratory, randomized, open-label, multicenter, phase 2 trial (PRESERVE 3; NCT04887831) is to assess whether trilaciclib administered with standard-of-care platinum-based CT and avelumab maintenance can improve antitumor efficacy and reduce CIM versus CT and avelumab without trilaciclib, in patients with locally advanced or metastatic urothelial carcinoma (mUC). Methods: Adult patients with measurable disease per RECIST v1.1, no prior systemic treatment for mUC, and ECOG performance status ≤2 will be randomized 1:1 to receive gemcitabine 1000 mg/m2 plus cisplatin 70 mg/m2 or carboplatin area under the curve 4.5 (± trilaciclib 240 mg/m2 IV over 30 minutes, ≤4 hours prior to CT) in 21-day cycles. Patients will receive 4–6 cycles of CT. Those without progressive disease per RECIST v1.1 can receive avelumab 800 mg maintenance therapy (± trilaciclib) in 14-day cycles until disease progression, unacceptable toxicity, investigator/patient decision, or end of trial. Patients will be followed for survival. The sample size was calculated to support the primary endpoint of progression-free survival (PFS), using a stratified log-rank test accounting for two stratification factors (visceral metastasis and platinum agent [cisplatin/carboplatin]). 63 PFS events will be required to achieve 77% power to detect a hazard ratio of 0.6 with a 2-sided significance of 0.2, corresponding to a median PFS of 11.7 months for the trilaciclib arm. Assuming a 10-month enrollment period, final PFS analysis approximately 22 months after the first randomization, and 5% loss to follow-up, 90 patients are required for randomization. PFS will be analyzed in the intention-to-treat population. Secondary endpoints include objective response rate, disease control rate, PFS during maintenance, OS, multilineage myeloprotective effects, and safety/tolerability. Exploratory endpoints will assess pharmacodynamic parameters, including those related to immune-based mechanisms, and efficacy by CDK4/6-dependence. Enrollment opened in June 2021. As of September 29, 2021, 8 sites are open, and 1 patient randomized. Clinical trial information: NCT04887831.

558 Background: The AA profile may be altered in malignancies and provide insights into tumor biology and the immune state. We hypothesized that the longitudinal AA profiling of mUC pts receiving an immune checkpoint inhibitor (ICI) may provide insights into the immune response, which may be associated with immune events and help discover new therapeutic targets. Methods: We utilized serum from mUC pts receiving an ICI or platinum-based chemotherapy (PBC) at the Dana-Farber Cancer Institute. Age and sex matched healthy controls were also studied. The SeroTag immuno-oncology discovery array (Oncimmune) was utilized, with quantification of the AA reactivity towards 1150 antigens. Bound autoantibodies were detected using an anti-IgG-specific detection antibody conjugated to the fluorescent reporter dye phycoerythrin. The AA reactivity was reported as the median fluorescence intensity (MFI) for each color and sample using a Luminex FlexMAP3D analyzer. A significance analysis of microarrays was performed to identify AAs with elevated levels in bladder cancer compared to matched healthy controls (HCs). AAs with > 1.5 increase between pre- and post-treatment were reported. Scatter and box-whisker plots were reported for all pts and antigens, respectively. Results: Pre- (n = 66) and post treatment (n = 65) serum samples were available from mUC pts receiving pembrolizumab (n = 25), atezolizumab (n = 21), nivolumab (n = 5), avelumab (n = 1), durvalumab + tremelimumab (n = 1), nivolumab plus vaccine (n = 1), and 12 pts who received PBC (cisplatin n = 8, carboplatin n = 4). The median duration between the pre- and post-therapy samples was 6 months, median age was 67.7 years (range 40-91) with 51 men (77.3%). Overall, significant heterogeneity of AAs between pts was observed with 37 AAs showing higher reactivity in pre-treatment mUC pts vs. 47 HCs, notably anti-CTAG1 (NY-ESO-1), CTAG2 (NY-ESO-2), MAGE B-18, KRAS, GRB2, RARRES2, HSP72 and FGFR3 (all p < 0.05). Pre- and post-therapy AA profiles were similar with unique changes seen in each patient. Notably, 3 pts receiving an ICI developed AAs to NY-ESO-1. Pts receiving PBC less frequently developed new AAs, although pts treated with cisplatin appeared to develop AAs more frequently compared to carboplatin-treated pts. Conclusions: This is the first report of a comprehensive AA profile using a novel platform in mUC pts. The study identified multiple elevated AAs in mUC pts vs. HCs, most notably NY-ESO-1, which also developed in some pts following ICIs. Pts treated with PBC did not develop new AAs frequently, although there appeared to be a difference between cisplatin and carboplatin-based chemotherapy. Further development of this platform is warranted to provide data that is orthogonal to genomic/transcriptomic profiling and shed insights on potential therapeutically actionable antigens.

565 Background: Metabolomic profiling of plasma from mUC pts has not been comprehensively examined. Plasma metabolomics may capture the effects of interactions between the malignancy, host and therapy. We hypothesized that Identifying metabolites in plasma from patients with mUC receiving an ICI or PBC may shed valuable insights regarding tumor biology and mechanisms of resistance. Methods: We obtained 0.2 ml plasma before and after starting therapy from pts with mUC receiving an ICI or PBC at the Dana-Farber Cancer Institute. Plasma metabolomic profiling was conducted at the Broad Institute using 3 complementary liquid chromatography tandem mass spectrometry (LC-MS)-based metabolomics platforms. We measured 648 metabolites at baseline prior to starting ICI/PBC and at a second time point in each subject following initiation of ICI/PBC. Metabolite levels were assumed to be normally distributed with log transformation to transform distributions to be approximately symmetric. We performed Wilcoxon-rank sum test to compare the levels of metabolites before and after initiation of the ICI or PBC (significance at p < 0.05). Results: Plasma was available at baseline and during therapy in 53 mUC pts (ICI: n = 43; PBC: n = 10). The median age was 68 (range: 39-86) years and 42 (82.3%) were male. The median time from baseline to the second time point was 4.7 months (range: 0.7-90.2). The ICIs administered were atezolizumab (n = 20), pembrolizumab (n = 16), nivolumab (n = 5), and durvalumab + tremelimumab (n = 1). We identified 20 metabolites that were significantly increased in post-PBC plasma samples (vs. pre-PBC) and 19 metabolites increased in post-ICI (vs. pre-ICI) samples (p < 0.05). All altered metabolites except one (Uracil) were exclusive for each treatment group. The most significant metabolites that increased following initiation of the ICI and PBC are shown in the Table. Evaluation of the association of plasma metabolomics with clinical outcomes and toxicities is ongoing. Conclusions: This is the first report, to our knowledge, of comprehensive metabolomic plasma profiling of pre- and post-ICI and PBC pts with mUC. The metabolomic changes after ICI appear distinct from those seen after PBC. Furthermore, our study sheds insights on potential mechanisms of resistance and new therapeutic targets in pts with mUC.[Table: see text]

481 Background: EV is an anti-Nectin-4 antibody-drug conjugate that has been approved by the US FDA for mUC progressing on platinum and PD1/L1 inhibitor therapy and in cisplatin-ineligible pts following prior therapy. However, prognostic and predictive biomarkers in the setting of EV therapy are unclear. We aimed to investigate baseline and early changes in commonly available clinical and laboratory tests that could help predict survival and toxicities in patients with mUC treated with EV. Methods: Data from patients with mUC who were treated with EV at Dana Farber Cancer Institute between 2017 and 2021 were reviewed retrospectively. We assessed the association of demographic (age, sex), clinical (ECOG-performance status [PS], sites of metastasis) and laboratory variables (hemoglobin, RDW, neutrophil count, lymphocyte count, neutrophil-to-lymphocyte ratio, platelet count and serum albumin) at baseline as well as after 4-7 weeks of treatment with Overall Survival (OS) by constructing univariate and multivariable Cox proportional-hazards models. Any variables significantly associated with OS at the univariate level (using an alpha-level of 0.1 to determine statistical significance) were then entered into the multivariable model. Predictors were eliminated from the final multivariable models by a backward selection process, retaining only those with a p-value of ≤ 0.05. Results: A total of 49 patients who received EV were included in the analysis. The median age was 72 years (range 48-88) and 36 (73.5%) were male. The median OS was 13.3 months (range: 2.7-38.7) and grade 3-4 toxicities were seen in 11 pts (22.4%). In the final multivariable models, lower serum albumin at 4-7 weeks (HR = 0.18; 95% CI = 0.05-0.71; p = 0.015), and baseline ECOG-PS of 1 vs. 0 (HR = 2.56; 95% CI = 1.05-6.21; p = 0.038) were significantly associated with worse OS (Table). Patients with higher serum albumin levels at 4-7 weeks also had significantly lower odds of experiencing grade 3-4 adverse events on EV (OR = 0.05; 95% CI = 0.002-0.52; p = 0.02). Conclusions: Lower serum albumin appeared to predict worse survival and severe toxicities in mUC pts receiving EV. This information may guide therapy and assist in the prevention of toxicities. Additionally, ECOG-PS was prognostic while the location of metastatic disease was not prognostic in the setting of EV.[Table: see text]

TPS591 Background: Neoadjuvant cisplatin-based combination chemotherapy improves survival in cisplatin-eligible patients (pts) with muscle invasive bladder cancer (MIBC). An unmet need exists in cisplatin-ineligible pts with MIUC who are offered upfront surgery. Neoadjuvant immune checkpoint inhibitors (ICIs) have been demonstrated to be safe and active although the benefit may not extend to the majority of pts. The combination of GCa and an ICI has been demonstrated to be safe and active in cisplatin-ineligible metastatic urothelial carcinoma. In the neoadjuvant setting, combination GCa and an ICI may improve outcomes across a broad group of MIUC by delivering early systemic therapy to pts with cisplatin-ineligible MIUC. We hypothesized that the combination of GCa and avelumab, a PD-L1 inhibitor, may improve pathologic complete remissions (pCR) and long-term outcomes compared to upfront surgery for MIUC (S2011, NCT04871529). Methods: This multicenter, randomized (1:1), open-label phase II trial is comparing the combination of GCa and avelumab (Arm A) as neoadjuvant therapy vs. upfront surgery (Arm B) for pts with cisplatin-ineligible MIUC including MIBC and high-risk upper tract urothelial carcinoma (UTUC). Adjuvant therapy following radical cystectomy, nephroureterectomy or ureterectomy is deferred to investigator discretion in both arms. Eligible pts include those with MIBC or high-grade UTUC with a predominant urothelial component who are cisplatin-ineligible (≥1 of: Zubrod performance status [PS] = 2, creatinine clearance [CrCl] 30 to < 60 ml/min, neuropathy > grade 1, hearing loss > grade 1, congestive heart failure > grade 2). The primary objective is pCR. The stratification factors include clinical stage (cT2N0M0 vs cT3-4aN0M0), Zubrod-PS (0-1 vs 2), CrCl (30 to < 60 vs ≥ 60 ml/min). With 178 evaluable pts, the trial will have a power of 90% (using a 1-sided alpha 0.05) to detect pCR rate improvement from 15% to 35%. The secondary objectives are toxicities, resectability rates, surgical complications, event-free survival (EFS) and overall survival (OS). Correlative studies include tumor molecular profiling, blood immune studies, circulating tumor-DNA profiling and radiomics. Arm A receives gemcitabine 1000 mg/m2 IV days 1, 8 every 3 weeks x 4 cycles, carboplatin AUC 4.5 (escalated to AUC 5 from cycle 2 if tolerated in cycle 1) IV day 1 every 3 weeks x 4 cycles and avelumab 800 mg IV day 1 every 2 weeks x 6 cycles. Surgery is performed 4-8 weeks after the last neoadjuvant administration. The trial is funded by NIH/NCI grants U10CA180888, U10CA180819, U10CA180821, U10CA180820, U10CA180868, and in part by EMD Serono, as part of an alliance between the healthcare business of Merck KGaA, Darmstadt, Germany (CrossRef Funder ID: 10.13039/100009945) and Pfizer. Clinical trial information: NCT04871529.