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THE QUESTION Can the most deadly form of skin cancer, melanoma, be prevented with sunscreen use?
THIS STUDY randomly assigned 1,621 adults who lived in a sunny climate to use sunscreen daily or whenever they wanted to for at least four years. Daily users were to put sunscreen with a sun protection factor (SPF) of 16 on their head, neck, arms and hands every morning and reapply it after heavy sweating, bathing or spending a long time in the sun. The others could use a sunscreen with any SPF; about 35 percent used it once or twice a week at most, and 38 percent never used it. Participants also took either a beta-carotene supplement or a placebo daily, to test whether the supplement might enhance protection. Sun exposure was found to be similar between the groups, as was their use of other means of sun protection, such as wearing a hat or seeking shade. Nearly 15 years after the start of the study, 11 melanomas had been detected among the daily sunscreen users, compared with 22 among the others, for a 50 percent reduction. Invasive melanomas were 73 percent less common in the daily-use group. Beta carotene showed no beneficial or harmful effect.
WHO MAY BE AFFECTED? Adults who spend time in the sun. Harmful exposure can occur in any season and at any temperature, wintertime included. The sun's ultraviolet rays penetrate the skin and damage cells, which can lead to skin cancer over the long term. Basal cell and squamous cell are the most common types of skin cancer, but melanoma is the most dangerous and is reportedly occurring with increasing frequency. Melanoma accounts for about 75 percent of skin cancer deaths.
CAVEATS Results might have been different if sunscreen users had been compared with those who never used it; the authors wrote, however, that asking a group to use a fake sunscreen would have been unethical. The effect on children was not tested.
FIND THIS STUDY Dec. 6 online issue of the Journal of Clinical Oncology (jco.ascopubs.org).
LEARN MORE ABOUT melanoma at www.cancer.gov and www.skincancer.org.
- Linda Searing
The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.
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