Incidence of New Primary Cutaneous Melanoma in Patients With Metastatic Melanoma Treated With Immune Checkpoint Inhibitors

Abstract

The development of new primary cutaneous melanoma (CM) after starting immune checkpoint inhibitor (ICI) therapy is poorly characterized. To determine the incidence of new CM in patients treated with ipilimumab, nivolumab, and/or pembrolizumab for metastatic melanoma. Single-center, retrospective, observational cohort study using an institutional database to identify patients diagnosed with melanoma at a tertiary care cancer hospital in New York, New York. Ipilimumab, nivolumab, and/or pembrolizumab treatment for metastatic melanoma. Primary outcomes were the incidence proportion, the incidence rate, and the 5-year cause-specific cumulative risk. A total of 2251 patients were included in the study; mean (SD) age at the time of ICI start was 62.8 (14.4) years. The majority were male (63.8%, n = 1437), White (92.7%, n = 2086), and non-Hispanic (92.1%, n = 2073). Forty-two of 2251 patients who received ipilimumab, nivolumab, and/or pembrolizumab were diagnosed with 48 new CMs at a median (range) of 397.5 (39-2409) days after ICI initiation. The median age of affected patients at the time of ICI first dose was 66.5 years. The majority were male (66.7%, n = 28), White (92.9%, n = 39), and non-Hispanic (100.0%, n = 42). There were no differences in age, sex, race, and ethnicity among patients who did and did not develop a new CM. Patients who developed a new CM were more likely to have a family history of melanoma (23.8% vs 16.3%, P = .02). Most new CMs (n = 30, 62.5%) were diagnosed after the last date of ICI administration. Twenty-seven (56.3%) new CMs were in situ and 21 (43.8%) were invasive. Of the invasive CMs with a reported Breslow thickness (n = 20), the median (range) thickness was 0.4 (0.1-8.4) mm. The overall incidence proportion of new CM was 1.9% (95% CI, 1.4%-2.5%) and the incidence rate was 1103 cases per 100 000 person-years (95% CI, 815-1492). The 5-year cumulative cause-specific risk of new CM was 4.9% (95% CI, 3.3%-7.4%). Patients treated with ICI therapy for metastatic melanoma remain at risk for the development of new CM.