It’s a glorious warm and sunny day today in London, UK. A shadow was cast, though, by this story which appeared today in one of the UK’s national newspapers. It concerns the tragic death of a 21-year-old lady from malignant melanoma. We’re told that that the victim ‘hated the sun’ and did her utmost to protect herself from it. Yet, she still ended up succumbing to malignant melanoma. The subtext: any amount of sun is hazardous.
However, is it true that ultraviolet exposure of the skin causes malignant melanoma? I know this link is constantly referred to and alluded to, but does it stand up to scrutiny?
In 2008, the British Medical Journal ran a piece by Dr Sam Shuster (a dermatologist) in which he dissects some pertinent research regarding the link between sunlight exposure and malignant melanoma . Here are some of the points made in this piece:
1. some forms of skin cancer (relatively harmless basal cell and squamus cell cancers) tend to occur in sun-exposed parts of the body, but 75 per cent of malignant melanomas do not.
2. The relationship with latitude is small and inconsistent (in other words, locations closer to the equator with more sunlight exposure do not see very significantly increased malignant melanoma incidence).
3. Malignant melanoma incidence and death from this condition are lower in individuals with increased sunlight exposure (11 studies are cited as evidence to support this).
4. Incidence of malignant melanoma is not reduced and can be increased by sunscreen use.
5. Melanoma risk associated with sunbed use is “small and inconsistent”.
6. Inducing malignant melanoma in the laboratory using ultraviolet light is difficult (in contrast to basal cell and squamus cell carcinomas).
In short, the relationship between sunlight exposure and malignant melanoma is far from clear-cut. More than this though, there is even some evidence that sunlight exposure might help protect against this condition.
It’s important, I think, to bear this in mind when reading stories like the one I link to above. The ‘sunlight at any dose is dangerous’ subtext comes from the belief that sunlight is a major cause of melanoma. This, quite frankly, appears not to be an accurate reflection of the truth. The balance of evidence suggests some protective effect. Taking this at face value, is it possible that this lady’s death was not in spite of her fear of the sun, but partly because of it?
We are faced with the very real possibility that this death was the result of general misinformation about the supposed perils of sunlight exposure.
See here for advice about how to get safe sun exposure.
1. Shuster S. Is sun exposure a major cause of melanoma? No. BMJ 2008; 337:a764