In people younger than 40 years, the combined rate of basal and squamous cell carcinomas increased by 74% from 1976 to 2003, Leslie J. Christenson, M.D., and colleagues have reported.
From 1976 to 1979, the combined incidence of basal and squamous cell carcinoma was 19/100,000. In 2000–2003, the rate had increased to 33/100,000.
The biggest increase occurred in basal cell carcinomas in women, wrote Dr. Christenson, a dermatologist at the Mayo Clinic, Rochester, Minn., and her associates. In 1976–1979, the incidence of basal cell carcinoma (BCC) in women was 13/100,000; by 2000–2003, it had risen to 31/100,000. Rates in men rose as well, but not as sharply (23/100,000 vs. 27/100,000) (JAMA 2005;294:681–90).
“These findings in young people really speak to the risk factors in this population,” study coauthor Randall K. Roenigk, M.D., said in an interview. “This is not due to people living longer and getting more sun exposure. These people are either getting more exposure, or the exposure they get is worse.”
The population-based study, which drew its data from the Rochester Epidemiology Project, wasn't able to draw associations between exposure and tumors. However, the study offered clues that seem to implicate tanning as one cause.
The head and neck are typically the most common sites of BCC and squamous cell carcinoma (SCC). Only about 60% of the tumors in this study occurred there—lower than the 80%–90% reported for the general population. Forty-one percent of the BCCs were located on the torso. “This change in location has been thought to support the etiologic factor of excessive outdoor tanning, use of tanning parlors, or both,” they wrote.
Of those BCCs on the torso, 48% were superficial, 36% were nodular, and 7% were aggressive. In contrast, of those tumors on the head and neck, 4% were superficial, 49% were nodular, and 24% were aggressive.
Squamous cell carcinoma rates increased as well, rising from 1/100,000 in 1976–1979 to 4/100,000 in 2000–2003. There were no significant rate differences between men and women.
The study, which excluded anyone with a genetic predisposition for skin cancer, casts doubt on the assumption that some of the recent increase in skin cancers is the result of people living longer and thus, having more cumulative sun exposure, said Dr. Roenigk, chairman of the dermatology department at the Mayo Clinic. “These people are under 40—they don't have that cumulative risk. This is behavior driven.”
Stay alert to the possibility of skin cancers in younger patients, Dr. Roenigk advised. “The bottom line is, we're going to see it in younger populations, and this curve will probably continue to rise as these people age, unless they change their behavior drastically.”