Anatomic location of primary melanoma: Survival differences and sun exposure

Background: Anatomic location of melanoma has been shown to independently influence melanoma-specific survival (MSS). Objective: We aimed to compare the MSS of specific anatomic subsites and between chronically, intermittently, and rarely sun-exposed sites. Methods: A prospective cohort study was performed of primary invasive cutaneous melanomas with known thickness and location reviewed at a tertiary referral center over 21 years. Results: Overall, 3570 primary cutaneous invasive melanoma cases were included. After adjustment for clinicopathologic variables (including thickness, ulceration, mitotic rate, sex, age, and subtype), posterior scalp melanoma was associated with worse MSS (hazard ratio [HR], 2.46; 95% confidence interval [CI], 1.38-4.40) compared with the upper back, whereas melanoma on the thighs, forearms/hands, and anterior upper arms had better MSS. Intermittent (HR, 0.56; 95% CI, 0.41-0.76) and chronically sun-exposed sites (HR, 0.70; 95% CI, 0.51-0.96) had improved survival compared with rarely exposed sites on multivariate analysis. Limitations: Potential selection bias of a tertiary referral center selecting for advanced cases. Conclusion: Altered MSS in the posterior scalp, thighs, forearms, hands, and anterior upper arms appears to be independent of clinicopathologic factors. Results were similar for both sexes and age groups. The posterior scalp should be considered a poor prognosis site.