Real-world time to next treatment in metastatic urothelial cancer patients: Enfortumab vedotin and pembrolizumab vs chemotherapy as first-line treatment.

707 Background: Since 2023, the combination of enfortumab vedotin and pembrolizumab (EV+P) has become a first-line (1L) non-chemotherapy (chemo) standard-of-care option for metastatic urothelial carcinoma (mUC). However, real-world (RW) data on clinical outcomes for EV+P remain limited. We evaluated RW clinical outcomes among patients (pts) with mUC treated with either EV+P or chemo in US community oncology practices in the 1L setting, as well as second-line (2L) utilization patterns of EV+P and chemo. Methods: We used the deidentified Integra PrecisionQ database to identify mUC patients initiating 1L EV+P or chemo after December 1, 2023. Index date was defined as the start of 1L therapy. Baseline pt characteristics collected include age at index date, sex, race, payer, ECOG performance status, and metastatic type (de novo metastatic disease vs. recurrent). Time to discontinuation (TTD) was defined as the time from the index date to 1L discontinuation or death. Time to next treatment (TTNT) was defined as the time from the index date to the date of any subsequent systemic treatment (2L) or death. Multivariable Cox proportional hazards regression modeling was performed to evaluate the association between treatment type and TTNT, adjusting for covariates. Adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) are presented. The distribution of 2L regimens was assessed for pts who initiated 2L therapy. Results: A total of 535 pts met study eligibility, of whom 406 (76%; median age [IQR]: 74 yr [67,81]) received EV+P as 1L therapy, and 129 received chemo (24%; median age [IQR]: 72 yr [65,79]). Overall, 91% of the cohort presented with de novo metastatic disease. The median follow-up for the study cohort was 4.7 mo (range: 0.03-18.9), during which 157/535 pts had died (EV+P: 117/406; chemo: 40/129). The table summarizes TTD and TTNT results. Of the 535 pts, 90 initiated 2L during the follow-up period, with most pts (32/46) who received 1L EV+P initiating chemo in the 2L setting. More than half of pts (24/44) who received 1L chemo received 2L EV+P. Conclusions: The adoption of EV+P as 1L therapy for mUC has been rapid since 2023 in US community oncology practices. Use of EV+P use was observed to be associated with longer time to 1L TTD and TTNT. Among pts who initiated 2L, EV+P treatment crossover between regimens is common. Median Time to Event (95% CI), mo Chemo (n=129) EV+P (n=406) logrank P value aHR for EV+P vs. chemo (95% CI) P value TTD 2.3 (1.9, 2.9) 5.9 (5, 7.5) <0.001 0.41 (0.31, 0.54) <0.001 TTNT 6.6 (3.3, 10.8) 9.7 (8.4, 10.6) 0.038 0.74 (0.55, 1.00) 0.051