BODY SITE DISTRIBUTION OF CUTANEOUS MALIGNANT-MELANOMA IN RELATIONSHIP TO PATTERNS OF SUN EXPOSURE

A study of all newly incident melanoma patients in British Columbia In 1991-1992 was undertaken to test the hypothesis raised by an earlier study, which showed that in younger patients the incidence rate of mel anoma per unit area of skin was higher on intermittently exposed skin areas than on continuously exposed areas. Using 1,033 patients and a m ore detailed body site categorisation than was previously possible, ou r results confirmed that in both men and women under age 50 the highes t melanoma density was on the back, At ages over 50, the greatest dens ity occurred on fully exposed sites, such as the face, though the dors um of the hand and forearm, likely also to have high exposure, show ve ry low melanoma densities. Differences between males and females corre late well with differences in likely exposure patterns. These results were seen for all invasive cutaneous melanomas combined; the patterns were similar for subtypes and for both invasive and in situ melanoma, with the exception of lentigo maligna melanoma (LMM), which occurs alm ost exclusively on the face, even at younger ages. Comparison with the earlier study (1976-1979) shows that the age-standardised rates for m elanoma excluding LMM have increased by 60%, with the greatest proport ional increase being at younger ages; in the recent data, the age-stan dardised rate for intermittently exposed sites exceeds that for usuall y exposed sites. Our results confirm that intermittent sun exposure ha s a greater potential for producing melanoma than continuous exposure at ages below about 50, though at older ages melanoma is more common o n body sites with continuous sun exposure. Int. J. Cancer 78:276-280, 1998. (C) 1998 Wiley-Liss, Inc.