Background: Several immune checkpoint inhibitor (ICI)-based combination regimens are standard-of-care for first-line treatment of metastatic renal cell carcinoma (mRCC). These include dual ICI and ICI-tyrosine kinase inhibitor (TKI) combinations. While single-agent ICI is recommended as subsequent-line therapy for ICI-naïve patients, there is limited knowledge regarding efficacy of rechallenging with a different ICI or using different ICI combinations in patients who have progressed on prior ICI therapy. This is a clinically critical question as most mRCC patients would have already received ICI therapy at progression. The aim of this study is to address the above by performing a systematic review and meta-analysis. Methods: PubMed, Cochrane Library and Web of Science were systematically searched to identify studies of later-line ICI rechallenge after progression on any previous ICI in mRCC patients from database inception to December 31^st, 2022. Patients who had progressed on prior ICI and rechallenged with ICI as single agent/dual/TKI combination as any subsequent line of therapy in both retrospective and prospective studies were included. Exclusion criteria were phase I or any phase studies combining ICI with unapproved drugs, case reports and case series. We calculated the pooled objective response rate (ORR) and disease control rate (DCR) using mixed effects model treating individual studies as a random effect. We further stratified studies into prospective and retrospective and performed subgroup analyses. Results: A total of 11 studies, 6 prospective and 5 retrospective with a total of 603 patients were initially identified. Out of the 6 prospective studies, 3 had an adaptive design of using salvage ipilimumab/nivolumab in patients who had either progressed or had stable disease as the best overall response on nivolumab monotherapy. These studies were excluded as they did not meet our inclusion criteria. A total of 8 studies with 400 patients were included in the final analysis. The ORR was 28% (95% CI, 0.27-0.36) and the DCR was 70% (95% CI, 0.47-0.85) with no significant differences between prospective and retrospective studies. Our ORR is higher than an earlier meta-analysis reporting an ORR of 14% with salvage ipilimumab/nivolumab after previous treatment with ICI. Conclusions: This meta-analysis demonstrates a modest ORR and an impressive DCR. Therefore, it provides strong clinical rationale to consider rechallenging with ICI-based therapy for later-line treatment of mRCC patients who have progressed on prior ICI.

*Studies were excluded because DCR was not reported.