An uncommon form of melanoma with a dismal prognosis, mucosal melanoma (MM) has a unique biology. There are few studies on the effectiveness of immune checkpoint inhibitors (ICIs). For a study, researchers evaluated the effectiveness of ICIs in MM, taking main site and ethnicity/race into account.

A retrospective cohort research including 25 cancer centers from Australia, Europe, the United States, and Asia was conducted. Anti-programmed cell death protein 1 (PD-1) ± ipilimumab was used to treat patients with histologically proven MM. Response rate (RR), progression-free survival (PFS), overall survival (OS), and survival by the primary site (naso-oral, urogenital, anorectal, other) as well as by therapy group (Caucasian, Asian, Other) were the primary outcomes. The Cox proportional hazards model was analyzed using single and multiple variables.

There were 545 patients altogether, of which 331 (63%) were Caucasian, 176 (33%) were Asian, and 20 (4%) were other. Among the primary locations were 206 (38%) naso-oral, 178 (32%) urogenital, 113 (21%) anorectal, and 45 (8%) other. Anti-PD-1 and anti-PD-1/ipilimumab were given to 348 (64%) and 197 (36%) patients, respectively. By the main site, ethnicity/race, or therapy, the RR, PFS, and OS were not different. Anti-PD-1/ipilimumab had a numerically greater RR for naso-oral (40%, 95% CI: 29% to 54%) than anti-PD-1 (29%, 95% CI 21% to 37%). About 35% of the patients who reacted at first made improvements. The median duration of response (mDoR) was 26 months (95% CI: 18 months–not attained). The Eastern Cooperative Oncology Group (ECOG) performance status (PS) more or around 3 (P<0.01), lactate dehydrogenase (LDH) levels over the upper limit of normal (ULN) (P=0.01), lung metastases (P<0.01), and more or around 1 prior therapies (P<0.01) were all related with a short PFS. LDH >ULN (P=0.03), lung metastases (P<0.01), ECOG PS ≥1 (P<0.01), and more or around 1 prior treatment (P<0.01) were all related to short OS.

MM’s prognosis was not good. The effectiveness of anti-PD-1 ± ipilimumab treatment was comparable and did not differ by ethnicity/race. Without affecting survival, the response to anti-PD-1/ipilimumab was statistically greater in naso-oral primaries. Ipilimumab was added, although it did not appear to be more beneficial than anti-PD-1 for other main locations. Short mDoR and frequently acquired resistance were seen in responders. Other elements, such as the location and quantity of metastases, are related to survival.