Association between stromal/TGF-β/EMT gene expression signature and response to pembrolizumab monotherapy in cisplatin-ineligible patients with locally advanced (unresectable) or metastatic urothelial carcinoma.

433Background: PD-L1 immunohistochemistry and an 18-gene T cell–inflamed gene expression profile (GEP) are associated with response to anti–PD-1/PD-L1 therapy across tumor types, including urothelial carcinoma. A gene expression signature representing convergent biology related to stromal/EMT/TGF-β pathways was developed and prespecified for testing for association with pembrolizumab response in urothelial carcinoma patients treated on the KEYNOTE-052 trial (NCT02335424). Methods: KEYNOTE-052 was a single-arm phase 2 trial of pembrolizumab in cisplatin-ineligible patients with previously untreated, advanced urothelial carcinoma. Primary objective of this analysis was to assess the association between the Stromal/EMT/TGF-β signature and outcomes (best overall response [BOR], PFS, OS) as an independent biomarker and to understand its potential prognostic/predictive role beyond the T cell–inflamed GEP score or PD-L1 assessed using combined positive score (CPS). Cox regression models for PFS and OS and a logi...