Although sunscreen use is widely assumed to protect against both sunburn and skin cancer, scientific evidence for the latter is scarce.
This could be for many reasons, including the protective spectrum of the products that are reflected in most of the studies which is significantly narrower than those found on the market today.
However, according to Professor Brian Diffey from the department of Dermatology at Newcastle University, UK, this lack of conclusive evidence to prove sunscreen efficacy should not stop us from recommending it as a preventative measure.
Recent meta-analyses of observational case control studies have demonstrated no association between sunscreen use and either the prevention of the development of malignant melanoma, writes the Professor in a recent article published in the British Journal of Dermatology.
This, he says, may be down to many factors that could confuse the results. “Sunscreens are more often used by those at risk of burning and those who are most likely to develop melanoma. On the other hand, sunscreen users may also use other methods of sun protection such as clothing and shade.”
New generation – better protection
In addition, the UV absorbing properties of earlier generation sunscreens was much lower than those currently on the market. Using a modern day SPF 25 product would cut the UV dose to the skin of around one-third of that experienced with earlier products, according to Diffey.
Furthermore, there is data to suggest that sunscreen use does that seem to reduce solar keratoses (markers of increased risk of melanoma) and melanocytic nevi (melanoma risk markers).
According to the professor, if we can estimate the increase in melanoma risk that we incur by lying in the sun on the beach without using a broad spectrum protection product and we know the usage rates of sunscreen within a population, it is possible to estimate the number of melanoma’s that could be avoided.
In his calculations, Diffey estimates that if lying in the summer sun with no protection raises the risk of melanoma by 20 per cent compared to using protection, then 24,500 of the 200,000 cases diagnosed in a year could be saved.
Obviously varying the usage rates and using different estimations of risk would lead to very different calculations, but Difffey concludes that the numbers are significant and following a precautionary principle, sunscreen use should be recommended.
“Given that appreciable numbers of melanoma cases would be avoided if modern sunscreens proved to provide even a very modest reduction in risk, it is argued that it would be irresponsible not to encourage their use,” he concluded.
Source: British Journal of Dermatology
2009, Volume 161, Issue 3, pages 25-27
Sunscreens as a preventative measure in melanoma: an evidence-based approach or the precautionary principle?
B.L. Diffey