Could sun exposure improve melanoma survival?

Solar ultraviolet radiation (UVR) exposure is clearly associated with increased mortality from non-melanoma skin cancer – usually squamous cell carcinoma. However, the association with cutaneous melanoma is unclear from the evidence in ecologic studies, and the few analytic studies that have been published show that high levels of intermittent UV exposure prior to diagnosis are associated with improved survival from melanoma. We had previously noted that histologic evidence of solar elastosis was inversely associated with melanoma mortality in five-year follow up of a cohort of melanoma patients in Connecticut. Using data from this population-based study of cutaneous melanoma, we calculated the hazard ratio for melanoma-specific mortality, using a competing risk analysis, accounting for death due to other causes as a competing risk. Other potentially confounding covariates, such as other measures of solar exposure, surveillance measures and clinical prognostic factors, were evaluated and controlled in analyses. In a multivariate analysis, taking into account competing risks for mortality, awareness of skin, lesion thickness, anatomic site of melanoma and mitotic index, solar elastosis was positively and significantly associated with survival (P < 0.01; Hazard Ratio 0.5, 95% Confidence Interval 0.3, 0.8). These analyses suggest that some factor associated with sun exposure, particularly the more objective measure evaluated in the original lesion biopsy — solar elastosis — may play a more complex role in the progression of melanoma than previously thought. Further studies should focus on replicating these results and on understanding more thoroughly the biological relationship of solar exposure to progression in melanoma.