Mucosal melanoma (MM) is a rare form of melanoma with poor survival outcomes. Data on treatment for MM is limited to results from studies on cutaneous melanoma or from small cohorts of MM patients. The Veterans Affairs population is one of the largest U.S. healthcare networks and includes individuals traditionally under-represented in clinical trials (older age and diverse ethnic and racial backgrounds). Using data from the Veterans Affairs will allow us to examine one of the largest cohorts of MM patients.

Immune checkpoint inhibitors (ICIs), specifically anti-programmed death-1 (PD-1) therapies (nivolumab and pembrolizumab) and anti-cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) (ipilimumab), have emerged as promising therapeutic candidates for treatment of MM, but studies have thus far yielded mixed results. A large-scale outcomes study in patients treated with immunotherapy may provide us with additional information to guide therapy choice based on real-world data.

Survival among MM patients varies by anatomical location, possibly due to anatomical surgical constraints, different lymphovascular supplies, different stages at diagnosis, different tumor mutational burdens, and different immune system characteristics by site. We will examine whether site of primary tumor predicts improved survival with ICI treatment.