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

Abstract

Mucosal melanoma (MM) is a rare melanoma subtype with distinct biology and poor prognosis. Data on the efficacy of immune checkpoint inhibitors (ICIs) is limited. We determined the efficacy of ICIs in MM, analysed by primary site and ethnicity/race. Retrospective cohort study from 25 cancer centres in Australia, Europe, USA and Asia. Patients with histologically confirmed MM were treated with anti-PD1+/-ipilimumab. Primary endpoints were response rate (RR), progression-free survival (PFS), overall survival (OS) by primary site (naso-oral, urogenital, anorectal, other), ethnicity/race (Caucasian, Asian, Other) and treatment. Univariate and multivariate Cox proportional hazard model analyses were conducted. In total, 545 patients were included: 331 (63%) Caucasian, 176 (33%) Asian and 20 (4%) Other. Primary sites included 113 (21%) anorectal, 178 (32%) urogenital, 206 (38%) naso-oral and 45 (8%) other. 348 (64%) received anti-PD1 and 197 (36%) anti-PD1/ipilimumab. RR, PFS and OS did not differ by primary site, ethnicity/race or treatment. RR for naso-oral was numerically higher for anti-PD1/ipilimumab (40%, 95% CI 29-54%) compared with anti-PD1 (29%, 95% CI 21-37%). 35% of patients that initially responded progressed. Median duration of response (mDOR) was 26 months (95% CI 18-NR [Not Reached]). Factors associated with short PFS were ECOG PS ≥3 (p<0.01), LDH >ULN (p=0.01), lung metastases (p<0.01) and ≥1 previous treatments (p<0.01). Factors associated with short OS were ECOG PS ≥1 (p<0.01), LDH >ULN (p=0.03), lung metastases (p<0.01) and ≥1 previous treatments (p<0.01). MM has poor prognosis. Treatment efficacy of anti-PD1+/-ipilimumab was similar and did not differ by ethnicity/race. Naso-oral primaries had numerically higher response to anti-PD1/ipilimumab, without difference in survival. The addition of ipilimumab did not show greater benefit over anti-PD1 for other primary sites. In responders, mDOR was short and acquired resistance was common. Other factors, including site and number of metastases were associated with survival.