Wednesday, March 23, 2005

Overcooked claims

'Based on current trends, children could be three times more likely than their grandparents to develop malignant melanoma', says BBC News, reporting the launch of a new campaign by Cancer Research UK. The concern is that climate change in the UK and greater numbers of foreign holidays mean that rates of melanoma will continue to rise in the future. Men and women born in 1970, now in their mid-30s, are being diagnosed with melanoma at the same rate as people who were born in 1930 and didn't develop melanoma until their 50s. The campaign contains advice on ways to reduce sun exposure. Professor Brian Diffey of Newcastle University told the BBC that public awareness campaigns would help lower the toll, but he emphasised that early detection was the key to bringing down mortality rates.

Barely two weeks after the last blizzards, the annual skin cancer campaign has begun. But does this campaign do any good?

It would be surprising if skin cancer rates in the UK did not rise to some extent. After all, people born in 1930 in the UK would rarely see strong sunshine. A year spent with British weather and smoggy skies would be relieved by a week or two in Blackpool or Margate. No danger of serious sunburn there. The mere fact of jetting abroad at all was always bound to have some effect on the pale British skin.

However, the relationship between sunbathing and melanomas is far from clear-cut. The most common forms of skin cancer (basal-cell or squamous-cell carcinomas) are definitely related to sun exposure. But they are also highly treatable and rarely serious. The relationship between malignant melanomas, which are much more serious, and sunlight is less clear. For example, melanomas tend to appear on areas of the body that are less likely to be exposed to the sun. Rates for melanoma in Japan are comparable to those in the UK, even though there is no tradition of sunbathing in Japan.

The explanation offered for this apparent contradiction is that cancers can be caused by one-off incidents of sunburn on holiday. But can the occasional bit of sunburn really cause cancer, or is this a case of trying to fit the facts to a shaky theory? While the British obsession with turning lobster-pink in Mediterranean resorts may lead to nasty sunburn (and the bafflement of the locals), it seems unlikely to cause cancer. Professor Jonathan Rees, head of the dermatology department at Edinburgh University, believes 'there is little hard evidence to support these public health campaigns in the UK' - a point that even Professor Diffey seems to have some sympathy with.

Moreover, there is some evidence now suggesting that vitamin D may have a protective effect against some cancers. Our bodies produce most of their own vitamin D through skin exposed to sunlight. In northern Europe during the winter, people get very little exposure to the sun, so a quick trip to the Costa del Suntan might be beneficial. While getting sunburnt regularly probably won't do you much good, the opposite reaction of avoiding the sun altogether is unlikely to be helpful either. The current campaign is based on an Australian model, but now the Cancer Council of Australia has said: 'A balance is required between avoiding an increase in the risk of skin cancer and achieving enough ultraviolet radiation exposure to achieve adequate vitamin D levels.'

We should remind ourselves that skin cancer is a relatively minor cause of death in the UK. Even if rates did treble, the chances of any individual developing a melanoma would still be quite small. The benefits of two weeks away are well worth such a tiny risk.

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