Comparative Efficacy of First‐Line Immune Checkpoint Inhibitor‐Based Combination Therapies in Patients With Sarcomatoid Renal Cell Carcinoma: A Japanese Multicenter Cohort Study

OBJECTIVES: Sarcomatoid renal cell carcinoma (sRCC) is an aggressive histological variant associated with a poor prognosis. While immune checkpoint inhibitor (ICI)-based combinations have become the standard of care, the optimal first-line regimen, specifically dual immunotherapy (IO-IO) vs. IO plus tyrosine kinase inhibitor (IO-TKI), remains controversial. We herein examined the real-world clinical outcomes of Japanese patients with sRCC. METHODS: We conducted a retrospective multicenter study on 46 patients with advanced or metastatic sRCC receiving first-line ICI-based combination therapy between January 2018 and December 2024 (IO-IO: n = 18; IO-TKI: n = 28). In a comparative survival analysis, three favorable-risk patients in the IO-TKI group were excluded to align risk profiles, focusing on intermediate/poor-risk groups (n = 43). The primary endpoint was overall survival (OS). RESULTS: In the entire cohort (n = 46), the objective response rate was numerically higher in the IO-TKI group (64.3%) than in the IO-IO group (50.0%) (p = 0.37). In the comparative analysis of intermediate/poor-risk patients (n = 43), progression-free survival (PFS) was slightly longer (p = 0.071), and OS was significantly longer (p = 0.016) in the IO-TKI group than in the IO-IO group. A multivariable analysis adjusted for IMDC risk categories showed favorable survival with the IO-TKI regimen (HR 0.37, p = 0.061). CONCLUSIONS: The present study indicates that first-line IO-TKI combination therapy represents a promising treatment option with a potential survival advantage over IO-IO therapy for Japanese patients with sRCC. However, due to the retrospective design and small sample size, reliably determining the comparative efficacy of these regimens remains challenging, and further validation is warranted.