“Any bad, blistering burn in your lifetime increases your risk for skin cancer,” — Dr. John Williams, Brigham and Women’s Hospital
For years now, I have been, shall we say, a rather haphazard sunscreen user. And I’m not alone — a fact that makes dermatologists apoplectic.
The American Academy of Dermatology, on its website, recently re-affirmed its message, saying that “scientific evidence supports the beneficial effects of proper sunscreen usage.”The American Cancer Society recommends using “a sunscreen with a sun protection factor (SPF) of 15 or higher.” The federal Centers for Disease Control and Prevention does, too.
But, in this era of evidence-based medicine, I have three nagging questions: How much need I really worry about skin cancer? How tightly linked are sun exposure and skin cancer? And how good is the evidence for the cancer-protective effect of sunscreens?
The answers, I have discovered, are complex, but are tipping me toward more diligent sunscreen use.
To be sure, skin cancer is not among the 10 leading causes of cancer deaths, according to 2006 projections by the American Cancer Society. But melanoma will strike 62,190 people this year and kill 7,910. It would kill many more if it weren’t caught and treated early. It’s also still rising, though more slowly than in the past.
Moreover, this year, there will be more than 1 million cases of basal and squamous cell cancers, which often occur in sun-exposed areas of skin, like the face, neck and hands. Most of these are curable because they, too, are usually caught early. But removing cancers, especially from the face, can be disfiguring.
Question number two: the sun exposure link.
For squamous cell cancer, that’s a no-brainer. “There is a very direct relationship between the amount of sun exposure over a lifetime and the development of squamous cell cancer,” said Marianne Berwick, chief of the division of epidemiology and biostatistics at the University of New Mexico.
Dr. Martin A. Weinstock, a Brown University dermatologist and chairman of the Skin Cancer Advisory Group for the American Cancer Society, said squamous cell cancer can be triggered by two kinds of ultraviolet light, UVB and, to a lesser extent, UVA. Moreover, actinic keratoses — reddish patches on the skin linked to sun exposure — are now seen as precursors to squamous cell cancer.
The links between sun exposure and the other two skin cancers are trickier to sort out.
“Nobody knows much about basal cell cancer,” said Berwick. But the “real mystery” is melanoma.
“There is definitely a debate about how much melanoma is linked to the sun. The majority of dermatologists feel it is partially linked to the sun,” said Dr. Rebecca Kazin, an associate professor of dermatology at Johns Hopkins University. “It has a large genetic component as well,” with melanoma often running in families.
In a combined analysis of three large studies published in the Journal of Clinical Oncology last year, Harvard researchers listed the risks for melanoma in the following order: Older age, male sex, family history of melanoma, high number of moles, history of severe sunburn, and light color hair. In other words, sun is one factor among many.
In addition to debating how big a role sun exposure plays in melanoma, researchers are also not sure what pattern of exposure confers the most risk. Some say it’s intermittent exposure – like when pale workaholics spend a week in the Caribbean scorching their skin. But age of exposure to the sun is important, too. When people migrate before age 15 from the rainy United Kingdom to sunnier Australia, they end up with a higher risk of melanoma, like native Australians, noted Weinstock. If they migrate later, their risk is low, like the British, suggesting that childhood exposure is a major factor.
And now, sunscreens. The evidence for sunscreen’s protective benefits varies depending on the type of skin cancer involved.
For squamous cell cancer, the evidence that sunscreen protects “is so strong that there is essentially no room for reasonable doubt,” said Weinstock of Brown. One persuasive study was a 1999 randomized controlled trial of nearly 1,400 people in Australia, which found that sunscreens were protective against squamous cell cancers.
For basal cell protection, Weinstock characterized the evidence for sunscreens as “substantial but indirect, and not sufficient to provide proof.” For melanoma, he said, the case for sunscreen efficacy “is strong, but not definitive proof.”
Over the years, European research has suggested that sunscreen use could actually increase the risk of developing skin cancer, perhaps because, by delaying sunburns, sunscreen use encouraged people to spend more time in the sun.
But at least for melanoma, a meta-analysis published in 2002 in the American Journal of Public Health looked at data on 9,000 people and concluded that there was no increased risk linked to sunscreen use. A separate review of 18 studies in 2003 went further, finding no relationship, good or bad, between sunscreen use and melanoma.
Further muddying the waters on sunscreens is a class action lawsuit now in Los Angeles Superior Court. The suit alleges that some sunscreen makers are misleading consumers with labels that promise protection against UVB and UVA light when their products only protect against part of the UVA spectrum. The suit also alleges that some products wear off faster in water than advertised.
But if you’re worried, all you have to do is make sure the sunscreen you buy contains titanium dioxide, zinc oxide or avobenzone, which protect against the whole UVA spectrum. Most brands do now.
Sunscreens clearly help prevent sunburns, and “any bad, blistering burn in your lifetime increases your risk for skin cancer, including melanoma,” said Dr. John Williams, a dermatologist at Brigham and Women’s Hospital.
So, here’s my new vow. It’s time to mend my ways. Skin cancer isn’t the biggest health hazard out there, but it’s one I can do something about with very little effort. Even if the evidence for sunscreen is imperfect, using it takes so little effort and money, that I’ll be slathering the stuff on. At the very least, it smells good and is a nice moisturizer.