Melanoma-sun link under the spotlight

Wednesday July 23rd, 2008

The link between sunshine and the deadliest skin cancer, melanoma, is questioned today by a British expert.

Writing on the website of the British Medical Journal, Professor Sam Shuster of Norfolk and Norwich University Hospital, UK, states that sun exposure is indeed linked to common forms of skin cancer, which are all virtually benign, but not to melanoma.

He believes that melanoma is more closely associated with ethnicity, and points out that that 75 per cent of cases occur in relatively unexposed sites such as the feet of dark-skinned Africans.

"Incidence is unaffected or increased by use of sunscreens and the effect of sunbed exposure is small and inconsistent," he writes. "Therefore, the effect of ultraviolet light can only be minimal, and the case against a major role is clear."

Professor Shuster also casts doubt on the supposed rise in melanoma rates. "The misdiagnosis of benign naevi [moles] explains the melanoma epidemic," he writes, concluding: "We know the sun makes us feel better, we need skin synthesis of vitamin D for our bones, ultraviolet light may protect against some forms of cancer, and it has important immunological effects."

On the other hand, Professor Scott Menzies of the University of Sydney, Australia, argues that melanoma is common on body sites receiving more sun exposure and in people who tend to burn rather than tan.

"Sun exposure is the main cause of the disease," he writes. "This statement is supported by multiple observations."

For example, the incidence of melanoma among young adults in Australia fell from 1983 to 1996, coinciding with strong public health messages to use sun protection. "Sun exposure is clearly a major cause of this disease," he concludes.

Shuster, S. and Menzies, S. W. Head to Head: Is sun exposure a major cause of melanoma? The British Medical Journal, published online July 23, 2008.

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