Histologic subtype and response to immune checkpoint inhibitor (ICI) therapy in advanced urothelial cancer (aUC).

Abstract

495 Background: Urinary tract cancer can be pure urothelial carcinoma (PUC) or variant UC (VUC, defined here as pure non-UC or mixed UC + non-UC); VUC often has a worse prognosis. Little is known about outcomes for patients (pts) with VUC receiving ICI. We hypothesized that VUC does not compromise ICI efficacy in pts with aUC. Methods: We performed a retrospective cohort study across 18 institutions. Demographic, clinicopathologic, treatment and outcomes data was collected for pts with aUC who received ICI. Pts were stratified to PUC vs VUC; VUC was further divided by histologic subtype, i.e. squamous, neuroendocrine (NE), etc. We compared overall response rate (ORR) using logistic regression, progression free survival (PFS) and overall survival (OS) using Kaplan-Meier and Cox proportional hazards; p<0.05 was significant. Results: 519 consecutive pts were identified; 405, 414 and 411 included in ORR, OS and PFS analyses, respectively. Demographics included mean age 69, 27% female, 66% ever smokers, 15% upper tract disease, 54% with extirpative surgery. ORR to ICI between pts with PUC and VUC was comparable (both 28%, p=0.86) without significant differences for individual subtypes vs PUC. Median OS for pts with PUC was 11.0 vs 9.9 mo for VUC (p=0.45), but only 3.7 mo for those with NE features (HR=3.01 [95% CI 1.63-5.57] vs PUC, p<0.001). Median PFS was 4.1 vs 5.2 mo for PUC vs VUC (p=0.46) and 2.8 mo for NE (HR=1.85 [95% CI 0.94-3.61] vs PUC, p=0.07). Conclusions: ORR to ICI and OS were comparable across histologic types; however, OS was shorter for tumors with NE features. VUC should not exclude pts from receiving ICI in routine practice and clinical trials.[Table: see text]