Single-agent anti-PD-1 or combined with ipilimumab in patients with mucosal melanoma: an international, retrospective, cohort study

•In MM, treatment efficacy of anti-PD-1 and anti-PD-1/ipilimumab is similar.•Thirty-five percent of patients who initially responded progressed with acquired resistance. The mDoR was 26 months.•Treatment response does not depend on primary site (naso-oral, urogenital, anorectal) or ethnicity/race (Caucasians, Asians).•Naso-oral primaries have higher RR to anti-PD-1/ipilimumab but no significant difference in survival over anti-PD-1.•At other sites, addition of ipilimumab does not appear to give greater benefit over anti-PD-1 for any endpoint.