Studies conducted in the last few years have suggested a connection between clinical outcomes and the time of immune checkpoint inhibitors (ICIs) infusion. However, few data are available regarding the differences between early and late time-of-day (ToD) administration in metastatic renal cell carcinoma (mRCC) patients receiving immunotherapy and immune-based combinations. In this meta-analysis, we aimed to fully investigate the influence of timing of administration on the efficacy of mRCC immunotherapy, by comparing early ToD versus late ToD dosing in this setting. The present systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA). Overall Survival (OS) was measured as Hazard Ratios (HRs) and 95% confidence intervals (CIs). Our search resulted in the identification of 1429 potentially relevant reports, which were subsequently restricted to four following independent evaluation of three authors. The pooled HR for OS in RCC patients receiving early ToD versus late ToD dosing was 0.62 (95% Confidence Interval, 0.50-0.72; p < 0.001). According to our findings, a statistically significant improvement in terms of OS for mRCC patients receiving early ToD administration compared with late ToD dosing was observed, with a reduction of death by 38%. Well-designed, randomized clinical and translational trials are required to clarify this issue and to establish recommendations for personalized treatments according to ToD.
