Clinical outcomes of first-line combination therapy with immune checkpoint inhibitor for metastatic non-clear cell renal cell carcinoma: a multi-institutional retrospective study in Japan

Background In metastatic clear cell renal cell carcinoma (ccRCC), recent studies have shown promising efficacy of immune checkpoint inhibitor (ICI) combination therapy. However, there are insufficient evidences about clinical efficacy and safety of ICI combination therapy in metastatic non-ccRCC (nccRCC). Methods We retrospectively investigated 44 patients treated with nivolumab plus ipilimumab (ICI + ICI group) or anti-PD-1/PD-L1 inhibitor plus tyrosine kinase inhibitors (TKI) (ICI + TKI group), and assessed clinical efficacy in both groups. Results Of all patients, overall response rate and disease control rate for ICI combination treatments were 36.3% and 75%, respectively. The median progression-free survival (PFS) and overall survival (OS) was 8.8 and 23.9 months, respectively. Multivariate analysis revealed that the presence of liver metastasis significantly affected worse PFS and OS (p = 0.035 and p = 0.049). Importantly, PFS and OS seemed similar in ICI + ICI group and ICI + TKI group (p = 0.778 and p = 0.559). Although the discontinuation rate of the combination therapy due to adverse effects in patients aged >= 75 years was significantly higher compared to that in patients aged < 75 years (45% versus 12%, p = 0.017), there were no significant differences in PFS and OS between two groups (p = 0.290 and p = 0.257, respectively). Conclusion This study confirms clinical benefit of ICI combination therapy for metastatic nccRCC patients in real-world settings. Furthermore, the effectiveness of combination therapy was comparable between patients aged < 75 and those >= 75 years with respect to clinical prognosis.