Genes Hike Melanoma Risk Even in Those Who Tan Well
TUESDAY April 21, 2009 -- If you have dark eyes, dark hair and tan easily, you might think you don't have to worry much about melanoma.
But new research shows that variations of a particular gene can raise the risk of this deadly skin cancer, even in people whose ability to tan may make them appear to be at low risk.
Having a variant of the melanocortin-1 receptor gene (MCIR) puts people who have dark hair, dark eyes and who tan easily at more than twice the risk of getting melanoma as those with similar complexions who don't have the variant.
"Traditionally, a clinician might look at a person with dark hair who did not sunburn easily and classify them as lower risk for melanoma, but that may not be true for all people in the population," said Peter Kanetsky, an assistant professor of epidemiology at the University of Pennsylvania School of Medicine and a co-author of research on the topic. "Just because you tolerate sun exposure fairly well doesn't mean that you're not at increased risk for melanoma."
The findings were to be presented Tuesday at the American Association for Cancer Research annual meeting in Denver.
The researchers examined 779 people with melanoma at the Pigmented Lesion Clinic at the University of Pennsylvania and 325 people who did not have melanoma. They analyzed the participants' MCIR variant status and had them fill out questionnaires about sun exposure, ability to tan and their physical appearance.
Previous research has identified more than 50 versions of the MCIR gene, about four of which have been linked to an increased risk for melanoma, Kanetsky said.
In the study, about 70 percent of the healthy participants had some variant of the gene, and nearly 27 percent had one of the four high-risk variants.
Among the participants with melanoma, about 78 percent had a gene variant and 43 percent had a high-risk variant.
Those who had dark eyes and an MCIR variant had a about a threefold greater risk of developing melanoma than did those with dark eyes but no variant. Those who did not freckle but who had the high-risk variant had an eightfold increased risk, and those who tanned moderately or deeply after repeated sun exposure had about twice the risk.
"They're finding that in people who are able to tan, who conceivably could have been educated not to worry about the sun, the presence of those variants does confer increased risk of developing melanoma, compared to those who do not have the MCIR variant," said Dr. David Fisher, chief of dermatology at Massachusetts General Hospital and a dermatology professor at Harvard Medical School.
Having a variation of the MCIR gene has been shown in prior research to be associated with having red hair, freckles and fair skin. It's also been associated with a higher risk of melanoma, even when adjusting for lighter skin tone, lighter hair and lighter eyes, Kanetsky said.
In this study, the MCIR variant in people with red or blond hair did not affect melanoma rates.
Researchers are not sure why the MCIR variant didn't seem to boost melanoma risk in the fair-haired group, but they suspect that other biological processes or genes could be at work, causing the increased melanoma risk.
Melanoma, the most serious form of skin cancer, is highly curable when caught early. In 2008, an estimated 8,420 people in the United States died from it, according to the American Cancer Society. There were about 62,000 new cases.
Currently, there is no commercially available test for MCIR variants.
The Skin Cancer Foundation has more on melanoma.
Posted: April 2009