P1-293 - Eight patients with mucosal malignant melanoma treated by nivolumab: a retrospective analysis in a single institution

Abstract

Malignant melanoma arising from the mucosa was very rare accounting for 1-8% of cutaneous origin, and 5-year survival rate of the advanced disease was estimated as around 30%. In Japan, the patients with advanced melanoma had received dacarbazine (DTIC) monotherapy, regarded as the tentative standard, but the prognosis was very poor. However, immune checkpoint inhibitors such as anti-PD1 monoclonal antibody, nivolumab, innovatively changed the treatment of advanced malignant melanoma. We analyzed retrospectively the efficacy and safety profiles of nivolumab monotherapy in 8 patients with mucosal malignant melanoma. The median follow-up was 13.7 months (range: 3.1-25.2 months). The median age was 70 years (range: 56-82 years), and 5 patients were male. The primary sites of mucosal malignant melanoma were head and neck (N = 4), esophagus (N = 2), and vagina (N = 2). All the patients received pretreatment of DTIC. The administration of nivolumab is ongoing for 3 patients (13-17 cycles). One patient is under follow-up observation after 30 cycles of nivolumab treatment. The rest have finished the administration in 4-14 cycles (median: 9 cycles). Two patients with PD died due to disease progression. The overall response rate was 37.5% (CR: 25.0%, PR: 12.5%). In addition, continued nivolumab treatment in the patients with SD lead to a durable response. The median progression-free survival was 10.2 months, and the median overall survival was not reached. As for adverse events (AEs), hypothyroidism (grade 1) was observed in 7 patients. Any immune-related AEs over grade 3 were not observed. It is suggested that the prognosis of patients with advanced mucosal melanoma was improved by nivolumab monotherapy. We will explore the biological features of nivolumab responders.