April 22, 2009 (Denver) -- Looks can be deceiving. New genetic research suggests that dark-haired people who do not sunburn easily may be at risk for potentially deadly skin cancer, too.
"There's been this whole idea of duality between light-complexioned people with red hair and a proclivity to burn in the sun as one group at high risk of melanoma, and a second group with dark hair who tan well and do not have to worry about being in the sun as a second group at low risk," says Peter Kanetsky, PhD, assistant professor of epidemiology at the University of Pennsylvania.
The new research suggests that even people who "have not been severely harmed by the sun may still be at increased risk of melanoma," he tells WebMD.
The findings were presented at the annual meeting of the American Association for Cancer Research.
Kanetsky and colleagues identified variants in the melanocortin-1 receptor (MC1R), a gene discovered in the mid-1990s that is associated with human pigmentation. Their study involved 779 people with melanoma and 325 healthy people.
Overall, the presence of certain genetic variants in MC1R was associated with a more than twofold risk of melanoma, but this risk was largely confined to those patients who had dark hair and dark eyes and tanned easily.
If people had dark hair and also inherited certain MC1R genetic variants, their risk for melanoma increased 2.4-fold. MC1R variants were associated with a 3.2-fold increased risk among those with dark eye color, an eightfold increased risk among people who did not freckle, and a 9.5-fold increased risk among people who tanned quickly without burning.
"In people with light skin, MCIR variants had null or little effect," Kanetsky says. About 10% of melanomas in dark-complexioned people may be associated with MCIR variants, he says.
A screening test for MC1R is not yet available.
Melanoma accounts for less than 5% of skin cancer cases but causes the majority of skin cancer deaths. In 2008, more than 62,000 new melanomas were diagnosed in the U.S., and an estimated 8,420 Americans died from the disease, according to the American Cancer Society.
Gene Test for Bladder Cancer
Also at the meeting, Texas researchers reported that genetic variations in the body's inflammation pathway may lower the likelihood of recurrence and improve the chance of survival in people with bladder cancer.
The American Cancer Society estimates that 68,810 new cases of bladder cancer were diagnosed in 2008. Yang and colleagues studied people with non-muscle invasive bladder cancer. Most cases of bladder cancers have not invaded the bladder muscle.
The usual treatment is surgery to remove cancerous tissue from the bladder combined with chemotherapy and immunotherapy with Bacillus Calmette-Guerin (BCG) delivered to the bladder.
Nearly three-fourths of patients relapse despite initial successful immunotherapy with BCG, Yang says.
To find out why some people respond to BCG and others don't, the researchers evaluated a panel of 59 variants in 35 major inflammation genes in about 600 people with non-muscle invasive bladder cancer.
"We found that the inducible nitric oxide synthase (iNOS) genetic variant was most significant," Yang says.
Only 22% of people with the iNOS variant relapsed compared with 46% of those who did not have this variance. People with the variant lived an average of six years vs. less than four years for those without the variant.
In a further analysis, the researchers found that people with fewer than three variants in the 35 major inflammation genes studied are at low risk of recurrence while those with five or more variants are at high risk. People in the high-risk group relapsed in an average of 13.5 months compared with more than 96.7 months in the low-risk group.
Urine Test to Monitor Bladder Cancer
Other researchers reported that they are a step closer to developing a urine test to aid in the diagnosis of bladder cancer and the detection of those who may be at risk for recurrence.
Researchers led by Gangning Liang, MD, of the University of Southern California, found that bladder cancer cells have two distinct genetic patterns, depending on whether they are invasive.
John S. Witte, PhD, of the Institute for Human Genetics at the University of California, San Francisco, says there's a huge need for a blood or urine test to monitor bladder cancer patients.
Such a test would avoid the frequent and invasive procedures that patients now have to undergo, he tells WebMD.
Currently, patients have to come in every two to three months for biopsies to check whether cancer has returned, Witte says. "Anything we can do to get away from these kinds of invasive tests would mean patients would be more likely to show up for screening and it would be easier to monitor them."