Outcomes in patients (pts) with advanced urothelial carcinoma (aUC) treated with enfortumab vedotin (EV) after switch maintenance avelumab (MAv) in the UNITE study.

Abstract

537 Background: MAv is approved in pts with aUC without progression (PD) on 1L platinum-based therapy (PBT). As pts in the pivotal EV trials had not received MAv after PBT, data on outcomes with EV post-MAv are limited. We examined outcomes with EV post-MAv in the multicenter retrospective UNITE study. We hypothesized that outcomes would be similar to published EV data. Methods: Pts who received sequential PBT, MAv, then EV monotherapy were included. Investigator-assessed observed response rate (ORR) was assessed for evaluable pts with scans after ≥ 1 cycle EV using χ2 test and logistic regression. Progression-free and overall survival (PFS, OS) were measured from EV start and assessed using ΚΜ method and Cox proportional hazards model. Results: Among 633 pts at 16 US sites, 49 received PBT and MAv then EV. Median age 72; 63% men; 96% Caucasian; 82% ECOG PS 0/1, 71% lower tract tumor; 65% pure urothelial histology; 71% visceral or bone mets; 33% Bellmunt score (BS) 2-3. In terms of PBT, 67% had cisplatin-based (cis); 26% carboplatin-based (carbo); 6% both cis- and carbo-based therapy. Best response to PBT was CR/PR/SD for 12% / 59% / 29% pts, respectively. Median time from PBT start to EV start was 8.5 months (mo) (3.9-21.2). Median follow up from EV start was 8.5 mo (95%CI 6.7-15.0). ORR to EV was 54%; median PFS and OS were 7.0 mo (95%CI 5.8-13.3) and 13.3 mo (95%CI 10.8-NR). Median PFS2 measured from PBT start until PD after starting EV or death was 17.5 mo (95%CI 15.2-22.5). Median OS from PBT start was 22.5 mo (95%CI 18.6-NR); 29% of pts remained on EV at data cutoff; 43% received subsequent therapy (Tx) after EV with median time to next therapy 6.4 mo (1.8-15.9). Outcomes did not differ among subgroups, except for improved PFS and OS in pts with BS 0-1 vs BS 2-3 (Table). Conclusions: Pts with aUC treated with EV after MAv had outcomes consistent with data for EV in PBT- and checkpoint inhibitor-refractory aUC. These data support the use of EV as third-line Tx after progression on MAv but should be validated in larger cohorts. [Table: see text]