ABSTRACT: Importance:Recently, new drugs have been approved for the first-line treatment of metastatic renal cell carcinoma (mRCC). Nivolumab plus ipilimumab significantly increases overall survival for intermediate- and poor-risk patients with mRCC. However, considering the high cost of nivolumab plus ipilimumab, there is a need to assess its value by considering both efficacy and cost. Objective:To evaluate the cost-effectiveness of nivolumab plus ipilimumab vs sunitinib in the first-line setting for intermediate- and poor-risk patients with mRCC from the US payer perspective. Design, Setting, and Participants:A Markov model was developed to compare the lifetime cost and effectiveness of nivolumab plus ipilimumab vs sunitinib in the first-line treatment of mRCC using outcomes data from the CheckMate 214 phase 3 randomized clinical trial, which included 1096 patients with mRCC (median age, 62 years) and compared nivolumab plus ipilimumab vs sunitinib as first-line treatment of mRCC. In the analysis, patients were modeled to receive sunitinib or nivolumab plus ipilimumab for 4 doses followed by nivolumab monotherapy. Main Outcomes and Measures:Life-years, quality-adjusted life-years (QALYs), and lifetime costs were estimated, at a willingness-to-pay threshold of $100?000 to $150?000 per QALY. Univariable, 2-way, and probabilistic sensitivity analyses were performed to evaluate the model uncertainty. Additional subgroup analyses were performed. Results:Nivolumab plus ipilimumab provided an additional 0.96 QALYs, at a cost of $108?363 per QALY. Sensitivity analyses found the results to be most sensitive to overall survival hazard ratio (0.63; 95% CI, 0.44-0.89) and mean patient weight (70 kg, range, 40-200 kg). Other variables, such as the cost of nivolumab plus ipilimumab (mean, $32?213.44; range, $25?770.75-$38?656.13), utility values for nivolumab plus ipilimumab (mean, 0.82; range, 0.65-0.98), and proportion receiving nivolumab in sunitinib arm (mean, 0.27; range, 0.22-0.32), had a moderate or minor influence on model results. Subgroup analyses demonstrated that nivolumab plus ipilimumab was most cost-effective for patients with programmed cell death 1 ligand 1 expression of at least 1% ($86?390 per QALY). Conclusions and Relevance:In this model, nivolumab plus ipilimumab was estimated to be cost-effective compared with sunitinib for intermediate- and poor-risk patients with mRCC at a willingness-to-pay threshold from $100?000 to $150?000 per QALY.