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.
Dr. Rigel presented his preliminary results at the annual meeting of the American Academy of Dermatology.
The study identified six independent risk factors, each of which increased the risk of malignant melanoma between two- and threefold. In addition to the outdoor summer job, the other five were history of blistering sunburns, red or blonde hair, marked freckling of the upper back, a family history of melanoma, and a history of actinic keratoses.
The study involved 300 consecutive patients with malignant melanoma who were compared with 302 age- and gender-matched controls. The average age of the patients was about 50 years, with a range from 18 years to the mid-70s.
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 found no increase in risk with increasing age. “The model tended to predict early on in life what was going to happen later in life,” he said.
The lifetime risk of melanoma in the U.S. population is about 1.5%, Dr. Rigel said. The presence of any one of the six risk factors increased this risk to 3%–5%.
The presence of two or more of the risk factors increases the lifetime risk 5–10 times over that of the general population. Those with three or more have a 10-fold to 20-fold increase in risk.
This study carries an important message to primary care physicians, Dr. Rigel said. “There's only 9,000 [U.S.] dermatologists. 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 and Johnson, Neutrogena, and LaRoche-Posay. He said that none of those were relevant to his presentation and the study was privately funded.