RESPONSE: Re: A Prospective Study of Pigmentation, Sun Exposure, and Risk of Cutaneous Malignant Melanoma in Women

The proposal put forward by Boniol et al. to further investigate the role of solaria in the development of cutaneous melanoma is interesting from an etiologic as well as a public health perspective. They hypothesize that solarium users will be more likely than nonusers to develop melanomas at habitually covered sites (such as the trunk) and will have higher nevus counts overall. The correspondence by Boniol et al. highlights the nature and intermittency of UV exposure as a driving force underlying the development of melanoma at anatomic sites. By contrast, we have approached this important issue from the perspective of personal susceptibility (1). Although the importance of UV exposure in the development of melanoma is well documented (2,3), the majority of Australians never develop melanoma despite considerable (and, in many cases, extraordinary) exposure to intense UV radiation, which underscores the importance of individual susceptibility. Clearly, these two views are not mutually exclusive and may ultimately be reconciled as our understanding of melanoma development unfolds. We wish to correct an apparent misconception in the correspondence of Boniol et al., that lentigo maligna melanoma is the only type of melanoma that occurs on the head and neck in association with chronic sun exposure. We found that patients with lentigo maligna melanoma and patients with head and neck melanomas other than lentigo maligna melanoma have very similar risk factor associations (1). Given that approximately 50% of head and neck melanomas are histologic types other than lentigo maligna melanoma (4), it is important to recognize that they are likely to share a similar causal pathway. We endorse the suggestion of Boniol et al. that further analyses of the Norwegian–Swedish Women's Lifestyle and Health Cohort Study (5) should be conducted, even though that large, well-conducted prospective study has the following limitations. First, the cohort is quite young and follow-up is short, and thus the full melanoma burden of the cohort is yet to be realized. This limitation is particularly important with respect to the anatomic distribution of melanomas in the cohort, as we predict that women with low nevus propensity (putative “UV-resistant” women) will have had insufficient exposure time to develop melanoma at routinely exposed sites. Second, the cohort is restricted to women, for whom patterns of dress, sun exposure, and the anatomic distribution of melanomas differ substantially from those of men. Finally, in that study, nevus counts were self-reported, and only asymmetrical nevi larger than 5 mm on the legs were counted. If theories about the genesis and evolution of large nevi through components of UV radiation hold true (6), such a selective measure of nevus burden will be biased toward identifying women with particular sun exposure histories. Despite these limitations, we support the approach suggested by Boniol et al. for stratified analyses according to the nevus counts of study participants, and we agree with them that the findings would be of considerable interest to melanoma researchers and public health policy makers.