Sex differences in immunotherapy outcomes and tumor-infiltrating immune cell profiles in patients with advanced renal cell carcinoma

Sex differences in the outcomes of advanced renal cell carcinoma (RCC) treated with immune checkpoint inhibitors (ICIs) and the profiles of tumor-infiltrating immune cells (TIICs) remain unclear. We retrospectively evaluated data from 563 patients with RCC receiving systemic therapy, including first-line dual ICI combinations (i.e., immunotherapy [IO]-IO), combinations of ICIs with tyrosine kinase inhibitors (TKIs) (i.e., IO-TKI), TKI monotherapy, and subsequent nivolumab monotherapy. Survival and tumor response were compared between the sexes in each treatment group, and TIIC profiles were compared using 116 RCC tumor samples analyzed by flow cytometry. Progression-free survival (PFS) was shorter in female than in male patients in the IO-IO (p = 0.0227) and nivolumab monotherapy (p = 0.0478) groups. Furthermore, sex remained an independent factor for shorter PFS after adjusting for covariates in the IO-IO (p = 0.0340) and nivolumab monotherapy (p = 0.0322) groups. In contrast, PFS was not significantly different between sexes in the IO-TKI or TKI monotherapy groups (p > 0.05). Overall survival and objective response rates were not significantly different between the sexes in any of the treatment groups (p > 0.05). Some TIIC populations, including that of CD8 + T cells (p = 0.0096), decreased to a greater extent in female than in male patients in the advanced-stage population. The effectiveness of ICIs on PFS was lower in female patients than in male patients, potentially because of the different profiles of the immune microenvironment, particularly the decreased number of CD8 + T cells in females.