Safety and efficacy of immune checkpoint inhibitors (ICI) in metastatic non-clear cell renal cell carcinoma (nccRCC): An institutional experience.

640 Background: ICIs have improved outcomes in clear cell RCC patients (pts), and emerging data suggest that they may be effective against nccRCC. nccRCC comprises ~25% of renal tumors and consist of a diverse group of diseases. Despite recent evidence, data regarding the efficacy of ICIs in nccRCC remain limited, especially among rarer nccRCC subtypes. Methods: We identified all cases of metastatic nccRCC that received at least one dose of ICI therapy at UT Southwestern Medical Center from 2014 – 2018. Baseline characteristics and IMDC criteria were evaluated at the time of ICI initiation. Outcomes included objective response rate (ORR) per RECIST v1.1 criteria, time to next treatment (TNT), and overall survival (OS). Immune-related adverse events (irAE) were graded per CTCAE 4.0 criteria. Survival estimates were evaluated using Kaplan Meier methods. Results: We identified 28 pts with metastatic nccRCC; 12 (42.9%) unclassified RCC (uRCC), 8 (28.6%) papillary RCC (pRCC), 3 (10.7%) chromophobe RCC (chRCC), 3 (10.7%) hereditary leiomyomatosis and renal cell cancer (HLRCC), 1 (3.6%) translocation RCC (tRCC) and 1 (3.6%) acquired cystic disease-associated RCC (ACD-RCC). 23 (82.1%) pts were intermediate or poor risk by IMDC criteria. In total, 13 (46.4%) pts received nivolumab monotherapy, and 15 (53.6%) in combination with ipilimumab. 12 (42.9%) pts received ICI in the first line. The median TNT and OS amongst all nccRCC subtypes was 4.9 (95% CI: 1.7-8.1) and 15.9 (95% CI: 5.9 – 25.9) months respectively. The ORR was 3/28 (10.7%), with 2 complete responses. All responses were restricted to the pRCC and uRCC subtypes. 11 (39.3%) pts experienced any irAE and 5 (17.9%) had a grade 3/4 irAE, including one case of grade 4 myocarditis. The median time to onset of an irAE was 1.9 months (Range: 0.1 to 12.0). At a median follow up of 10.8 months (95% CI: 10.2 – 17.9), 4 pts remain on therapy and 13 pts have died. Conclusions: ICI therapy demonstrated modest efficacy in this cohort with comparable irAE profiles to ccRCC. Objective responses were not seen in pts with HLRCC, ACD-RCC, tRCC, or chRCC in this study.