Real-World Treatment Duration With First-line Enfortumab Vedotin Plus Pembrolizumab for Advanced Urothelial Cancer: A National Electronic Health Record Study.

BACKGROUND: Enfortumab vedotin plus pembrolizumab (EV+P) received accelerated approval (AA) from the US Food and Drug Administration in April 2023 for cisplatin-ineligible patients with advanced urothelial cancer (aUC), followed by full approval (FA) in December 2023 regardless of cisplatin eligibility. While clinical trial data demonstrate durable treatment exposure, real-world treatment patterns after approval in large, multi-institutional populations remain less well characterized. We evaluated real-world time on treatment (rwToT) with first-line EV+P in a large US oncology network. METHODS: We conducted a retrospective cohort study using deidentified patient-level electronic health record-derived data from the Flatiron Health database, representing approximately 280 US cancer clinics. Included were patients with aUC initiating EV+P between April 5, 2023 and January 30, 2025. Follow-up extended through April 30, 2025. We summarized characteristics of EV+P users using descriptive statistics and computed time on treatment using the Kaplan-Meier method. A prespecified subgroup analysis evaluated patients initiating therapy between AA and FA to approximate a primarily cisplatin-ineligible population with longer potential follow-up. RESULTS: Five hundred ten aUC patients initiated first-line EV+P after AA. Median age was 74 years and 75.7% were male. Approximately, 61.2% met real-world criteria for cisplatin ineligibility. At data cut-off, 60.4% (308/510) had discontinued EV+P, most commonly due to death (52.6%, 162/308), followed by initiation of second-line therapy (30.2%, 93/308), and treatment gap exceeding 60 days (17.2%, 53/308). Median rwToT was 7.5 months (IQR, 6.4-8.7). In the AA to FA subgroup, median rwToT was 7.1 months (IQR, 5.5-8.9). Among patients receiving subsequent therapy post EV+P, platinum-gemcitabine was the most common regimen (39.8%, 37/93). CONCLUSIONS: In this large US cohort of primarily cisplatin-ineligible patients, rwToT with first-line EV+P approximated that observed in clinical trials, though modestly shorter. These findings likely reflect the greater clinical frailty of patients treated in routine practice. Continued follow-up will be needed to evaluate long-term outcomes and treatment sequencing following EV+P adoption.