Good results come from the combination of nivolumab and ipilimumab in patient with recurrent small cell lung cancer (SCLC) with high tumor mutation burden (TMB). The combo induces an objective response rate (ORR) of 46% in patients, according to an exploratory analysis from the phase I/II CheckMate-032 study. The ORR was 21% with nivolumab monotherapy. The results were presented at the World Long-term Cancer Conference in Yokohama. CheckMate-032 is an ongoing, open-label, phase I/II trial evaluating the safety and efficacy of 3 mg/kg of nivolumab monotherapy or 1 mg/kg of nivolumab plus 3 mg/kg of ipilimumab in advanced or metastatic solid tumors. Treatment is delivered every 3 weeks for 4 cycles or until disease progression or unacceptable toxicity. The trial includes both PD-L1 expressors and non-expressors. The primary endpoint was ORR assessed by a blinded independent central review. Secondary objectives included safety, OS, progression-free survival (PFS), and duration of response. Biomarker analysis was an exploratory objective. Investigators did not present any new safety data in this analysis. Overall, in the pooled intent-to-treat (ITT) population (n = 401), the ORR was 11% with nivolumab alone and 22% with the combination. Among the ITT population, 211 (53%) patients had an evaluable TMB result for these analyses and were divided into subgroups of high, medium, and low levels of TMB. One-year PFS was 30% in patients with high TMB levels who received the combination. The 1-year PFS rates with the combination were 8% in patients with medium TMB levels and 6% for those with low TMB levels. With single-agent nivolumab, the 1-year PFS rates were 21% and 3% for patients with high and medium TMB, respectively. PFS was not evaluable in patients with low TMB.