SAN FRANCISCO — People who worked at outdoor summer jobs as teenagers for 3 years or more had twice the risk of developing malignant melanoma later in life as those who did not, according to a case-control study by Dr. Darrell S. Rigel of New York University Medical Center.
The study identified six independent risk factors, each of which increased the risk of malignant melanoma between two- and threefold, Dr. Rigel said in presenting preliminary results at the annual meeting of the American Academy of Dermatology.
Besides an outdoor summer job, the other five risk factors were history of blistering sunburns, red or blonde hair, freckling of the upper back, family history of melanoma, and a history of actinic keratoses.
The study involved 300 consecutive patients with malignant melanoma who were seen at Dr. Rigel's clinic. They were compared with 302 age- and gender-matched controls seen for acne, psoriasis, eczema, or other reasons unrelated to pigmented lesions. The average age of the patients was about 50 years, with a range from 18 years to the mid-70s.
Dr. Rigel and his colleagues evaluated all patients for the presence of 43 potential risk factors. Only six emerged as independent risk factors in a multivariate analysis.
In an interview, Dr. Rigel said there was at least one potential risk factor that was conspicuous by its absence from that list: The study showed no increase in melanoma risk with increasing age. “The model tended to predict early on in life what was going to happen later in life,” he said.
The presence of any one of the six risk factors increased the lifetime risk to 3%–5%. The lifetime risk of melanoma in the U.S. population is about 1.5%, he noted.
The presence of two or more of the risk factors increased the lifetime risk of melanoma 5–10 times over that of the general population. Those with three or more of the risk factors have a 10-fold to 20-fold increase in the risk of melanoma.
“You want to come up with a model that focuses as effectively as possible on those at high risk,” Dr. Rigel said. “Eventually, if you think about it, these are not the models we want. We're using surrogates. We're using factors that are not really the cause. The cause is genetic susceptibility and exposure to UV. … I believe that 5 or 10 years from now we'll have a genetic screen for melanoma.”
According to Dr. Rigel, this study carries an important message for primary care physicians. “There's only 9,000 dermatologists [in the United States]. Only one-third of dermatologic disease is treated by dermatologists. That means two-thirds are going to [primary care physicians]. We want those melanomas to be detected early. So models like this may let the primary care physician also focus on who they should focus their efforts on.”
Dr. Rigel disclosed financial relationships with Graceway, Pharmaderm, Johnson & Johnson, Neutrogena, and LaRoche-Posay. He said that none of those were relevant to his presentation, and that the study was privately funded.
Sun exposure during adolescence is predictive of melanoma later in life. ©