Australian researchers have gathered the first direct scientific proof that using sunscreen helps prevent skin cancer in those at highest risk.
Rubbing on sun-blocking cream has long been recommended as a way to protect the skin from the sun's harmful effects, including cancer. But this advice had been based on anecdotal evidence and animal experiments.
Now, researchers at the University of Melbourne have conducted a summer-long experiment showing that people who used sunscreen before going outside cut their chances of developing the first signs of skin cancer.
"It's the first time we have been able to definitively show that sunscreen lowers the risk of getting skin cancer later in life," said Dr. Darrell Rigel of New York University Medical School.
The study was conducted on 588 men and women who were randomly assigned to use either SPF-17 sunscreen or a look-alike dummy lotion from September, 1991, through March, 1992, one Australian summer. All already had from one to 30 solar keratoses--small, wart-like growths that are forerunners of skin cancer.
The Melbourne team, whose study was published in today's New England Journal of Medicine, found that the sunscreen users averaged a net loss of about half a keratosis, whereas those in the comparison group gained one.
About 700,000 Americans are diagnosed annually with skin cancers that are easily treatable. About 32,000 get melanoma, which spreads quickly and is deadly unless recognized early. Over the past 20 years, the incidence of melanoma has increased about 4% a year, and too much sun exposure is usually blamed.
In the study, the volunteers were instructed to put sunscreen on their heads, necks, arms and hands every morning and to reapply it during the day, if necessary.
Some researchers have argued that the use of sunscreen increases the risk of cancer by giving a false sense of security that encourages people to remain in the sun longer than they otherwise would. In this study, however, subjects were advised to avoid the sun as much as possible and to wear protective clothing.
Even though the subjects' exposure was probably relatively modest, the sunscreen clearly cut the risk of precancerous growths. Further, the more diligently participants applied it, the better it worked.