Are Immune Checkpoint Inhibitors (Ici) A Valid Option For Papillary Renal Cell Carcinoma (Prcc)? A Multicenter Retrospective Study.

582 Background: pRCC is the most common non-clear cell RCC (nccRCC) and represents up to 15% of RCC. Pivotal studies evaluating ICI mostly excluded nccRCC. Therefore the efficacy of ICI in pRCC remains to be demonstrated. Methods: We retrospectively investigated the activity and safety of PD-1/PD-L1 inhibitors (PD-1i) specifically in patients (pts) with metastatic pRCC from 15 centers in France and Belgium. Pts baseline characteristics, treatment outcome and safety were collected. Primary endpoint was time-to-treatment failure (TTF). Secondary endpoints included objective response rate (ORR), overall survival (OS) and treatment-related adverse events (TRAEs). Results: From 02/2016 to 09/2018, 50 pRCC pts treated with PD-1i were included. Median age was 63 years (range: 27-84), 36 (72%) were male. Histology included 14 (28%) type 1 pRCC, 30 (60%) type 2 pRCC, 6 (12%) unclassified pRCC. PD-1i was used in first line setting in 5 pts (10%), in second line in 29 pts (58%) and in third line or beyond in 16 pts (32%). IMDC risk group at PD-1i start was 22% good, 44% intermediate and 33% poor. ICI used were PD-1 inhibitors in 47 pts (94%) and PD-L1 inhibitors in 3 pts (6%). PD-1 in was used as monotherapy in 94% of pts. With a median follow up of 10.7 months (95% Confidence Interval (CI): 6.8-14.8), the median TTF was 3.7 months (95% CI: 3.1, 10.1). In type 1, the median TTF was 7.1 months (95% CI: 3.2-NA) and 3.2 months (95% CI: 2.9-NA) in type 2. Median treatment duration was 3.2 months (range: 0.4-24.5, IQR: 2.4-6.4). Among the 45 pts evaluable for ORR, best response was complete response/partial response in 8 pts (16%), stable disease in 13 pts (26%) and progressive disease in 24 pts (48%). ORR was 25% in type 1 pRCC and 15% in type 2 pRCC. Median OS was 17.6 months (95% CI 11.4- not reached). TRAEs of grade 3-4 were noted in 6 patients (12%) which led to treatment discontinuation, no grade 5 were observed. Conclusions: This retrospective study is the largest cohort of metastatic pRCC treated with PD-1i to date. PD-1i exhibit limited activity in this pRCC population, with better TTF and ORR in type 1 pRCC. Our findings underline the need for further prospective clinical trials evaluating ICI combinations in pts with pRCC.