Primary genitourinary melanoma: Epidemiology and disease-specific survival in a large population-based cohort

BACKGROUND: Primary genitourinary (GU) melanoma is a rare disease, which is poorly characterized. OBJECTIVE: To examine clinical characteristics and survival outcomes of primary GU melanoma among men and women. DESIGN, SETTING, AND PARTICIPANTS: Retrospective study using the Surveillance, Epidemiology, and End Results database (1973-2010) was used to identify primary GU melanoma cases by tumor site and histology codes. We examined associations of GU melanoma with demographic, clinical, and pathologic characteristics, as well as disease-specific survival (DSS). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: DSS was calculated using the Kaplan-Meier method. Cox-proportional hazard models were used to calculate hazard ratios and 95% CI for factors associated with worse DSS. RESULTS AND LIMITATIONS: A total of 1,586 histologically confirmed cases of primary GU melanoma were identified with a median age of 66.1 years (IQR: 55-80). Incidence of primary GU melanoma was 0.2cases/million among men and 1.80cases/million among women. Overall, 60.1% of patients had localized disease at presentation and 90.5% of patients had cancer-directed surgery. Patients with urothelial melanoma had the worst 5- and 10-year DSS (39% and 29%, respectively). Women with vulvar/vaginal melanoma had worse 5- and 10-year DSS compared to men with penile/scrotal melanoma. In multivariate analysis, decreased survival was associated with increasing age, distant stage, and lymph node involvement. Results are limited by the lack of standardized staging for primary GU melanoma and the retrospective design of our study. CONCLUSIONS: Patients with primary GU melanoma present with advanced stage and have a poor prognosis. Women have worse DSS compared to men. DSS is negatively associated with advanced age at diagnosis, higher stage, and lymph node involvement. PATIENT SUMMARY: Clinicians and patients must be aware of the poor disease-specific outcomes associated with primary GU melanoma. Most importantly, women fare worse than men and mucosal melanomas have worse outcomes compared to cutaneous melanomas.