Long-term Real-world Survival Outcomes with Dual Immune Checkpoint Blockade in Synchronous Metastatic Renal Cell Carcinoma: Implications for the Design of Prospective Cytoreductive Nephrectomy Trials.

Background and objective: Patients with synchronous metastatic renal cell carcinoma (s-mRCC) increasingly undergo systemic therapy with their primary tumour in situ. We report long-term survival outcomes and deferred cytoreductive nephrectromy (dCN) rates in an unselected real-world s-mRCC cohort of patients treated with nivolumab + ipilimumab. Methods: This was a retrospective cohort study of 287 patients with s-mRCC treated with nivolumab + ipilimumab between 2018 and 2024 at five European institutions. Data were collected for International mRCC Database Consortium (IMDC) risk, overall survival (OS), progression-free survival (PFS), treatment responses, and dCN rates. Key findings and limitations: At median follow-up of 23.5 mo, median OS was 29.0 mo (95% confidence interval [CI] 20.1-36.2) for the overall cohort ( Conclusions and clinical implications: Real-world treatment of s-mRCC with nivolumab + ipilimumab yields encouraging OS, especially in patients with intermediate IMDC risk and CR/nCR at metastatic sites. Trials investigating dCN following immunotherapy may be impacted by this lower-than-expected event rate, which could potentially affect their estimated sample sizes. Patient summary: We looked at outcomes for patients with metastatic kidney cancer who were treated with immunotherapy while their kidney tumour was still in place. Patients who responded well to immunotherapy were likely to survive for a long time, whether or not they then had surgery to remove their kidney tumour. Our results will help in the design of analyses for clinical trials that are already testing the role of delayed surgery for metastatic kidney tumours.