Clinical outcomes of nivolumab plus ipilimumab in patients with metastatic non-clear cell renal cell carcinoma: Real-world data from a Japanese multicenter retrospective study

Objectives: Although nivolumab plus ipilimumab has become a standard treatment regimen for metastatic clear cell renal cell carcinoma (ccRCC), its efficacy in non-clear cell carcinoma (nccRCC) has not been fully examined. In the current study, we evaluated the clinical outcomes of nivolumab plus ipilimumab in nccRCC compared with ccRCC.Methods: We retrospectively analyzed 22 patients with metastatic and/or locally advanced unresectable nccRCC who received nivolumab plus ipilimumab as a first-line therapy and compared them with 107 patients with ccRCC. Objective response rate (ORR), progression-free survival (PFS), overall survival (OS), and toxicity were compared between the nccRCC and ccRCC groups.Results: The histology of nccRCC included eight papillary, six unclassified, three chromophobe, two collecting duct carcinoma, and three other subtypes. Best objective response in nccRCC patients included three complete responses and five partial responses, resulting in an ORR of 36%, while that in ccRCC patients was 50% (p = 0.22). With a median follow-up of 11.9 months, OS was significantly shorter in patients with nccRCC than in those with ccRCC (median 20.8 months vs. not reached, p = 0.04), while there was no significant difference in PFS (median 6.3 vs. 10.8 months, p = 0.21). Treatment-related adverse events occurred in 14 (64%) nccRCC patients and 81 (76%) ccRCC patients.Conclusions: Combination treatment with nivolumab and ipilimumab demonstrated modest clinical efficacy in patients with nccRCC compared with patients with ccRCC, suggesting it could be a therapeutic option for metastatic nccRCC patients.