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April’s issue of The Scientist magazine will be out in ten days, and it’s a cancer special. You’re in for a treat, and there’s a super article by Keith Flaherty on melanoma, the deadliest form of skin cancer.

While prepping some material for the issue I came across an intriguing evaluation in F1000: Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up 10.1200/JCO.2010.28.7078. Hang on, I thought. Didn’t we know that sunscreen reduces melanoma incidence? After all, there is a clear correlation between exposure to sun, or sunbed use, and melanomagenesis.

Apparently not. While it would seem obvious that sunscreen should protect against melanomas, it’s a highly controversial issue. Regular sunscreen use does prevent cutaneous squamous cell carcinoma in long term, but the melanoma trials just hadn’t been able to give a clear result. There have been case-control and cohort studies, but non-randomized studies are “uable to distinguish the main determinants of sunscreen use from those of melanoma, because they are the same—namely, susceptibility to sunburn, high occupational or recreational sun exposure, and family history.”

So in this paper we have a “follow-up of a community-based, pragmatic trial of sunscreen to prevent skin cancer in Queensland, Australia.” And there’s a striking difference–sunscreen does appear to have a beneficial effect (although to be fair, it’s not statistically very powerful).

What’s really needed of course is a trial in children–intense sun exposure and burns are strong risk factors– but as F1000 Members Ryan Sullivan and Keith Flaherty point out,

It is unlikely, however, that such a study would be performed given the ethical dilemma of randomizing children to not receive sunscreen intervention in Australia.

Quite. You’ll just have to trust me on the sunscreen.