Sunscreen Alone Can’t Protect From Deadliest Skin Cancer

As summer approaches, scientists have a new warning for sun worshipers: sunscreen can’t completely protect you from the deadliest of skin cancers.

While high-protection sunscreen helps against most damage, enough radiation can get through to spur malignant melanoma, according to a study released yesterday in the journal Nature that’s the first to pinpoint a molecular mechanism of malignant melanoma, a disease that kills almost 10,000 Americans a year, according to the Skin Cancer Foundation.

Until now, exactly how ultraviolet rays damage DNA in skin cells hasn’t been clear. The researchers found the radiation harms a critical gene, called TP53, that normally helps heal broken DNA, preventing tumor progression. While use of heavy-duty sunscreen on mice limited the harm, it didn’t eliminate it, said Richard Marais, the study author.

“It’s the first experimental evidence that sunscreen actually protects you from melanoma but it also shows that it doesn’t offer complete protection,” said Marais, the director of the Cancer Research U.K. Manchester Institute. “You need to use other strategies as well.”

The TP53 gene, which wasn’t thought to be important in inhibiting melanoma before, coordinates with other DNA mutations that are estimated to cause almost half of deadly incidences of the skin cancer, the researchers said.

While mice protected with SPF-50 creams developed fewer tumors than unprotected mice, some still developed the disease, according to the study.

Many Misconceptions

There are a number of misconceptions surrounding the use of sunscreen, said Jonathan Silverberg, a dermatologist at Northwestern University Feinberg School of Medicine, in a telephone interview.

Patients think they only need to apply sunscreen once a day, when patients out at the beach with intense sun exposure need to reapply every two to three hours. If they’re sweating profusely or swimming, they need to apply it once every hour to two hours, he said.

“Skin cancer is the most common cancer in the United States. Period,” Silverberg said. “Melanoma is the fastest growing cancer in the United States and in many cases, around the world.”

To contact the reporter on this story: Sonali Basak in New York at sbasak7@bloomberg.net

To contact the editors responsible for this story: Reg Gale at rgale5@bloomberg.net Andrew Pollack

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