Outcomes with enfortumab vedotin in patients with advanced urothelial carcinoma and histology variants: Analysis of the UNITE study.

Abstract

652 Background: Enfortumab vedotin (EV) is approved for patients (pts) with advanced urothelial carcinoma (aUC) but outcomes in pts with histology variants (HV) have not been well described. We hypothesized that presence of HV would impact EV treatment outcomes. Methods: UNITE is a multi-site retrospective study of pts with aUC treated with targeted agents, including 650 pts treated with EV regimens. We compared outcomes to EV monotherapy in pts with pure UC (pUC) relative to pts with any HV and with specific HVs. In pts with scans after > 1 cycle of EV, observed response rate (ORR) was assessed using χ2 test and logistic regression. Median progression-free survival (PFS) and overall survival (OS) from EV start were measured using the Kaplan Meier method and Cox proportional hazard test. Results: A total of 566 pts (366 with pUC; 200 with HV) from 17 US sites were treated with EV monotherapy. Median age was 70 years, 71% men, 87% Caucasian, 74% with ECOG PS 0/1 and 28% with liver mets. Median follow up was 21 mos from EV start, ORR was 49%, mPFS and mOS were 5.8 mos (95% CI: 5.29-6.67) and 12.2 mos (95% CI: 11.5 – 13.8), respectively. Pts with pUC had more visceral mets (69% vs 60%, p = 0.04) and liver mets (32% vs 21%, p =0.003) than pts with HV. No significant difference in outcomes were seen between pUC and pts with HV component (1-100%). Pts with predominant HV (50-99%; N=35), had numerically lower ORR relative to pUC pts (36% vs 52% OR 0.31, p <0.09), but no difference in mPFS or mOS. Pts with pure HV (pHV) (100%: N=14) had inferior outcomes relative to pts with pUC (ORR 0% vs 52%, p<0.001; mOS HR: 2.96 (95% CI: 1.60 – 5.46), p <0.001; mPFS HR: 1.9 (95% CI: 1.06 – 3.39), p=0.03). ORRs for specific HV are listed in the table. No significant difference in treatment outcomes were seen in pts with pUC vs any specific HV, except for NE HV which had inferior ORR (0% vs 52%; p=0.003). Conclusions: Responses to EV are noted in some aUC pts with HV, except for NE (any component) and pHV. Certain HV notable for poor outcomes, such as sarcomatoid and plasmacytoid, demonstrated responses to EV. These hypothesis-generating findings require further validation in studies with adequate sample size for specific HV, and in particular pHV. Evaluation of biomarkers, including Nectin4 expression, in HV is paramount. [Table: see text]