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FRIDAY, June 13, 2003 (HealthDayNews) -- People who are genetically prone to melanoma are also much likelier to have a second gene mutation that leaves them susceptible to sun exposure.
Swedish scientists say the discovery of this genetic double whammy could help health professionals identify those at high risk for the cancer.
"The genetic mutation is not very common, but it is very important to inform these individuals who carry this mutation, and then to give them support and counseling to let them know what the research means and how to protect themselves," says study author Dr. Johan Hansson, director of the melanoma unit at Stockholm's Karolinska Hospital.
The results appear in a recent issue of the Journal of the National Cancer Institute.
The genetic mutation of a tumor-suppressing gene called CDKN2A occurs in approximately 20 percent of the 10 percent of melanoma cases where there is a family history of the disease, Hansson says. There are, however, different types of mutations of the same CDKN2A gene, the study adds, and here researchers looked at only one type.
Melanoma affects about 54,000 Americans annually, according to the American Cancer Society, and while it accounts for only 4 percent of skin cancers, it causes 79 percent of deaths from skin cancer.
For the study, researchers looked at 35 melanoma patients -- 25 with a family history of the disease who carried the mutation of the CDKN2A gene, and 10 with no hereditary association with melanoma. They compared the presence between the two groups of a mutation called NRAS proto-oncogene, which is related to sun exposure and is known to be associated with melanoma.
They found that while only 10 percent of those with no family history of the disease had NRAS mutations, 95 percent of those with the genetic mutation of the CDKN2A gene also had the NRAS mutations.
"We were surprised because the results were so striking," Hansson says. Of the group with the mutation of the CDKN2A gene, 20 out of 21 of those patients with a primary melanoma, which means the site where the cancer was first found, also had the NRAS mutations, compared with only one of the 10 patients with primary melanomas who had no genetic mutation.
A further important finding, Hansson says, is that all but one of the melanomas in the first group were found on sun-exposed parts of the body, suggesting there was an association between ultraviolet light exposure and activation of the NRAS mutations. The other primary melanoma, which means the site where the cancer started, was on the sole of the foot.
"This is certainly an important area to watch. People have been looking for these genes for a long time. Epidemiology studies have shown that one of the most important risks for melanoma is a family history of the disease," says Dr. Vincent DeLeo, an associate professor of clinical dermatology at Columbia University in New York City.
He adds, however, that there could be other gene mutations besides the one looked at in this study that are also associated with NSRA mutations.
The authors acknowledge their study examined mainly those with a specific genetic mutation for the CDKN2A, and that further work is needed to compare the NSRA mutations among patients belonging to families with other CDKN2A mutations as well as those with normal CDKN2A genes.
More information
For an explanation of skin cancer, with illustrations, visit the American Cancer Society. To find out if you're at risk for melanoma, go to the American Academy of Dermatology.
