HealthDay News — The incidence of pediatric malignant melanoma in the United States has increased 2% per year since 1973, reaching a rate of 6.0 per 1 million in 2009, study results indicate.
However, sun exposure did not appear to be the driving risk factor, according to Jeannette R. Wong, MPH, of the National Cancer Institute in Rockville, Md., and colleagues.
Low exposure to the UV-B rays due to living in northern latitudes, female sex and being aged 15 to 19 years were all associated with the greatest increases in incidence, they reported in Pediatrics.
Tanning bed use may help explain these trends, the researchers hypothesized, as indoor tanning use originated in the 1970s and is popular among this age group.
To better describe the incidence trend of childhood and adolescent melanoma Wong and colleagues analyzed data from 1,230 white young people, aged 20 years and younger from the Surveillance, Epidemiology, and End Results (SEER) database. All patients had a primary malignant melanoma recorded in nine cancer registries from 1973 through 2009. Data from other ethnic or racial groups was excluded due to the overall small number of melanomas reported in these populations.
Age-adjusted melanoma incidence increased during the study period by an average 2% per year among boys and 2.2% per year among girls, the researchers found.
Girls were 1.6 times more likely than boys to develop melanoma — with an incident rate of 7.4% vs. 4.6%. This gender disparity was consistent across all age groups.
Overall melanoma incidence increased with age from 1.1 cases per million before age 10, to 3.6 per million among 10- to 14-year-olds and 18 per million among those aged 15 to 19 years.
Although registries that included patients high UV-B areas further south generally reported a higher incidence of childhood melanoma, the trend for changes in pediatric melanoma rates was the opposite. Patients in areas with high UV-B exposure had stable melanoma rates over time, whereas those in low UV-B exposed areas experienced a 3.7% annual increase in incidence during the study period.
When the researchers analyzed increases in cancer incidence by body part, they found that tumor sites commonly occurred in sun-exposed areas, with annual increases of 4.5% per year for the skin on unspecified parts of the face, 2.8% for the trunk and 2.6% for the lower limbs and hip.
“Melanoma incidence continues to increase from previous studies, especially in adolescents and sun-exposed areas of the body with some evidence for geographic variation,” the researchers wrote. “Future individual-level studies are needed to elucidate the underlying reasons for the increasing incidence of adolescent melanoma.”
The study had several limitations, including lack of data on individual outdoor UV exposure, indoor tanning, familial risk factors, or the thickness of the patients’ lesion. The researchers were unable to draw inferences about causes of the trends, and were unable to rule out an influence of changes in diagnosis patterns during the study period.