Clinical features of vulvar and vaginal malignant melanomas and the effects of immune checkpoint inhibitors in Japanese patients: a single-center, retrospective cohort study

Vulvar and vaginal melanomas (VVMs) are rare malignancies, but they are relatively more common among Asian women. This makes the collection of data on VVMs in this population crucial. Moreover, no cohort studies have examined and compared the effects of immune checkpoint inhibitors (ICIs) on VVM in Asian women. Therefore, we aimed to investigate the clinical characteristics of VVMs in Japanese women and the effects of ICI treatment. This single-center, retrospective cohort study included patients who were histologically diagnosed with VVM at our hospital between March 2005 and December 2023. The Kaplan-Meier analysis was used to compare the prognosis of vulvar melanoma (VuM) and vaginal melanoma (VaM) throughout entire treatments and compare the efficacies of ICIs and conventional chemotherapies in VVM. In total, 28 women with VuM ( n = 14) and VaM ( n = 14) were included. There were no significant differences in overall survival (OS) [median OS: not reached (95% confidence interval (CI), 13.2-NA) vs. 30.2 months (95% CI, 23.2-NA), log-rank test, P = 0.456] between the VuM and VaM groups. The progression-free survival (median progression-free survival: 14.7 vs. 5.2 months, P = 0.002) and OS (median OS: 33.8 vs. 7.2 months, P < 0.001) were significantly better for the ICI-treated group than for the conventional chemotherapy-treated group in VVM. The prognosis of patients with VVM improved significantly with the advent of ICI, demonstrating the importance of ICI in the treatment of VVM.