Cancerous Vacations?

The development of dark moles—known as melanocytic nevi—are the best predictor of whether an individual will eventually contract melanoma, the most deadly form of skin cancer. Sun exposure is the primary environmental cause of those melanocytic nevi. A new study now finds that among 2,189 German children between the ages of 6 and 7, nevi counts correlated best with a history of vacationing in a sunny locale with a high solar-ultraviolet-light index.

The higher the UV index, the higher the melanocytic nevi count, Olaf Gefeller of the University of Erlangen-Nuremberg, Germany, and his coworkers report in the May 15 American Journal of Epidemiology.

Where might one encounter a high UV index? At southerly locations, such as Mediterranean beaches. At high altitudes, such as alpine ski resorts. Or in even mid-latitude cities during the height of summer.

In contrast to many other studies, total sun exposure alone did not prove a good predictor of nevi risk. For instance, exposures at home didn't raise risks, not did vacation exposures at northern, sunny sites. The findings suggest, the researchers conclude, that "exposure to intense intermittent doses of UV radiation induced by frequent vacations early in life shows a strong association with [large mole] development."

In the past, history of severe childhood sunburns has proven a somewhat useful risk factor for malignant melanoma. However, teasing out the importance of other sun exposures has proven more difficult, the researchers note. The new study's large size and the children's common hometown made it fairly easy for the researchers to attribute differences in nevi development to difference in vacation sites.

The message these data really bring home is the importance of slathering a child with sunscreen if intense sun exposures—even relatively brief ones—are expected.