5029 Background: With the recent approvals of checkpoint inhibitors (CPIs), a fibroblast growth factor receptor (FGFR) inhibitor, and an antibody-drug conjugate, patients with platinum-refractory metastatic urothelial carcinoma (mUC) have several treatment options available. However, many patients with platinum-refractory mUC need novel therapies after progressing on current therapies. We assessed the role of early phase trials in treatment of mUC and the impact of genomic alterations on their outcomes. Methods: We retrospectively analyzed medical records of patients with mUC who received an investigational therapy at the phase 1 clinic and had CLIA-certified clinical next generation sequencing. Clinical parameters and mutations were abstracted. Progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan-Meier methods. Hazard ratios (HR) were calculated using the Cox proportional hazard model. Results: Among the 57 pts enrolled in 41 unique phase 1 trials between 2015 and 2019, 16% (9/57) had variant histology: neuroendocrine carcinoma (n = 3) and urachal carcinoma (n = 6). Median age was 64. Majority were males (72%). 97% received prior platinum therapy and 60% had received prior CPI therapy. Across the pure urothelial carcinoma cohort (n = 48), median PFS was 4.2 months (m), median OS was 9.8 m, and the overall response rate (ORR) was 19%. TP53, FGFR, TERT, and ARID1A alterations (alt) were detected in 54%, 41%, 21% and 17% of UC patients, respectively. Patients harboring a TP53 alt, compared to no alt, had a shorter median PFS of 3.2m vs 9.6 m (HR = 2.738 [1.247 - 6.011], p = 0.0121). On the contrary, median PFS was longer in FGFR alt, compared to no alt, 6.3m vs 3.2m (HR = 0.4662 [0.224 - 0.971], p = 0.0415). Of note, 64% of FGFR alt patients were treated under an early phase FGFR targeting trial. Median OS was numerically longer in FGFR alt and shorter in TP53 alt but did not reach statistical significance (table). Conclusions: Patients with mUC may derive clinical benefit from enrollment in phase I clinical trials. Patients with TP53 alterations had numerically worse outcomes. Patients with mUC should be considered for an FGFR targeting therapy in the setting of an FGFR alteration. [Table: see text]
OC-0682: Phase 1 trial of pembrolizumab with SBRT in metastatic urothelial carcinoma
