No doubt: sun causes melanomas

Jul 22 2008

A leading University of Sydney researcher writes in the prestigious British Medical Journal today that claims that the sun is not the key cause of melanomas are false.

Professor Scott Menzies, director of the Sydney Melanoma Diagnostic Centre, argues that melanoma is far more common on body sites receiving more sun exposure and in people of races who tend to burn rather than tan.

In the same article, Sam Shuster, a consultant dermatologist at Norfolk and Norwich University Hospital, argues that while sun exposure causes the most common forms of skin cancers, there is no conclusive evidence that ultraviolet radiation from the sun causes the rarer and more serious malignant melanoma.

He argues melanoma is related to ethnicity rather than skin pigmentation, and in 75 per cent of cases occurs on relatively unexposed sites, especially on the feet of dark skinned Africans.

But according to Professor Menzies there is considerable evidence that intermittent sun exposure and sunburn are strong independent indicators of the risk of developing melanoma in white populations. "There is a clear association of increasing cases of melanoma and increasing environmental ultraviolet light," he says.

He also cites genetic evidence, with the major genes causing melanoma showing ultraviolet light "signature" mutations. He adds that people deficient in repairing ultraviolet light genetic damage have a 1000 times greater risk of developing the disease.

Professor Menzies also writes that data from Australia shows that cases of melanoma among young adults fell between 1983 and 1996, and this coincided with strong public health messages to use sun protection.

"When you examine the geographical, sun exposure and genetic evidence together, sun exposure is clearly a major cause of melanoma, he concludes.

The debate is published in the BMJ Online today.