Incidence of malignant melanoma by anatomic site, gender, and geographic location : an unanticipated trend

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Rdesinski, Rebecca E.
Oregon Health & Science University
Melanoma -- epidemiology; Ultraviolet Rays
thesis / dissertation description
The incidence of malignant melanoma has increased over the past 60 years in the United States. Since the early 1950s, evidence has been accumulating to link solar ultraviolet (UV) radiation to melanoma and it is now commonly accepted as a causal factor. Patterns of exposure to solar UV radiation and sun burns may contribute dissimilarly to the risk levels for malignant melanoma (MM) by gender at different anatomic sites. The head may be covered by hats and hair; the arm & shoulder, trunk, and leg & hip may be covered by clothing. Additionally, sun screen may be differentially applied to these areas of the body. The objective of this research is to generate exposure-response relationships by anatomic site and gender. We performed an ecologic analysis using population-based data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute and UV Index data from the National Weather Service. The analysis was restricted to Caucasians less than 76 years of age whose MM was diagnosed during 2000-04 in 14 SEER Cancer Registries in the contiguous United States, not including Hawaii. Cases totaled 39,582. The exposure-response relationships by anatomic site were significantly different between men and women. Incidence of MM in males exceeded females’ at all anatomic sites, except for the leg & hip. In linear regression analyses stratified by gender, age-adjusted incidence rates decreased with increasing average annual cumulative UV Index for all anatomic sites, except for male head (face, lip, eyelid, scalp, neck, ear) and male leg & hip. Incidence rates were lower in registries with greater annual cumulative UV Index days, suggesting that other factors associated with geographic residence may now be playing a larger role in risk. Such as, skin cancer prevention awareness and protective behaviors having more success in the “Sun Belt”. Therefore, people living in northern latitudes of the US should be counseled regarding their potential increased risk of MM occurring in typically covered anatomic sites. They should avoid behavior that may increase the risk of MM, particularly intermittent sunburns. Providers in northern latitudes should be as suspicious of skin lesions on the trunk, shoulder & arm, and leg & hip as they would be in southern locations.