Real-world analyses of therapy discontinuation of checkpoint inhibitors in metastatic melanoma patients

The 'real-world' patient population of metastatic melanoma is not fully represented in clinical trials investigating checkpoint inhibitors. We described therapy discontinuation in an unselected population-based cohort of adults with metastatic melanoma who started therapy with pembrolizumab, nivolumab, or nivolumab/ipilimumab from January 2015 to August 2017. Therapy discontinuation was defined as a gap between doses beyond 120 days, and/or initiation of another cancer therapy. We estimated drug-specific rate ratios for therapy discontinuation adjusted for age, sex, comorbidities, health care use, and past cancer therapies. We included 876 metastatic melanoma patients initiating pembrolizumab (44.3%), nivolumab/ipilimumab (31.2%), and nivolumab (24.5%). At 12 months of follow-up, the probabilities of therapy discontinuation were 49.9% (95% confidence interval, CI 43.6-56.5) for pembrolizumab, 58.8% (95% CI 50.5-67.3) for nivolumab, and 59.2% (95% CI 51.7-66.8) for nivolumab/ipilimumab. Stratified analyses based on prior cancer therapy, brain metastases at baseline, and sex showed similar trends. In multivariable analyses, compared with pembrolizumab, patients starting nivolumab (rate ratio 1.38, 95% CI 1.08-1.77) or nivolumab/ipilimumab (rate ratio 1.30, 95% CI 1.02-1.65) were more likely to discontinue therapy. Our findings indicate frequent discontinuations of checkpoint inhibitors at one year. The lower discontinuation associated with pembrolizumab should be confirmed in further studies.