Given the wide public health implications of the melanoma epidemic, ultraviolet radiation (UVR) exposure patterns contributing to cutaneous melanoma development should be clearly identified. To describe time trends of anatomic sites of melanoma using a UVR exposure model based on clothing and sun habits, we reviewed the medical records of all patients diagnosed with primary invasive melanoma or melanoma in situ (MIS) during the years 1977-78, 1983-84, 1989-90, 1995-96, and 2000-01 (n=3058) in one healthcare region of Sweden. Age-standardized incidence rates and relative risks (RRs) of melanoma by calendar period were estimated for intermittent and chronic UVR exposure sites. From 1977-78 to 2000-01, the incidence rates of all melanomas at intermittent UVR exposure sites increased both among men (7.8-16.5/10 person-years) and among women (7.6-14.6/10 person-years), with a sex-adjusted and age-adjusted RR of 2.1 [95% confidence interval (CI) 1.8-2.4, Ptrend<0.0001]. This increase was evident for both invasive melanoma and MIS. Melanoma at chronic sites increased among men from 1.7 to 2.3/10 person-years, and among women from 1.4 to 1.8/10 person-years, with a corresponding adjusted RR of 1.4 (95% CI 1.0-1.9, Ptrend=0.01), driven primarily by MIS. For melanomas at intermittent UVR exposure sites, the male sex was positively associated with central (core) areas (chest, back, neck, shoulders, thighs; RR 1.7, 95% CI 1.5-1.9), but negatively associated with peripheral areas (lateral arms, lower legs, dorsum of feet; RR 0.3, 95% CI 0.3-0.4), compared with the female sex. Sex-specific intermittent UVR exposure patterns drove the observed increase in melanoma incidence, whereas chronic UVR exposure contributed less.

The prognostic value of detailed anatomic site and ultraviolet radiation (UVR) exposure patterns has not been fully determined in cutaneous melanoma. Thus, we reviewed medical records for detailed site in a population-based retrospective Swedish patient cohort diagnosed with primary invasive melanoma 1976-2003 (n = 5,973). We followed the patients from date of diagnosis until death, emigration or December 31 2013, and evaluated melanoma-specific survival by subsite in a multivariable regression model adjusting for established prognostic factors. We found that melanoma on chronic UVR exposure sites (face, dorsum of hands; adjusted HR 0.6; CI 0.4-0.7) and moderately intermittent UVR sites (lateral arms, lower legs, dorsum of feet; HR 0.7; CI 0.6-0.8) were associated with a favorable prognosis compared with highly intermittent sites (chest, back, neck, shoulders and thighs). Further, melanoma on poorly visible skin sites upon self-examination (scalp, retroauricular area, back, posterior upper arms and thighs, buttocks, pubic area; HR 1.3; CI 1.1-1.5) had a worse prognosis than those on easily visible sites (face, chest, abdomen, anterior upper arms and thighs, lower arms and legs, dorsum of hands and feet, palms). In conclusion, highly intermittent UVR exposure sites and poor skin visibility presumably correlate with reduced melanoma survival, independent of established tumor characteristics. A limitation of the study was the lack of information on actual individual UVR exposure.

Trunk melanomas were associated with multiple lymph drainage, but the worse prognosis of trunk melanomas could not be explained by the increased frequency of multiple or uncommon SNLs.

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