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Frequent skin cancers might indicate increased risk for other cancers

People who develop abnormal numbers of skin cancers called basal cell carcinomas may be at increased risk of other, unrelated internal cancers.

There's no denying summer sun can be both glorious and deadly. Coming from a family of pathetically light-skinned people, I've been told all my life that careful and repeated applications of sunscreen are necessary to prevent the sun's ultraviolet rays from damaging our skin's DNA and causing cancer.

Unfortunately, it's nearly impossible to completely avoid harmful sun exposure. Fortunately, one of the most common types of skin cancer — a version called basal cell carcinoma — is highly treatable. About one in three Caucasians will develop at least one basal cell carcinoma in their lifetime. But a few people seem particularly susceptible.

Now dermatologist Kavita Sarin, MD, PhD, and medical student Hyunje Cho have uncovered a surprising correlation between frequent basal cell carcinomas and the likelihood of developing other, unrelated cancers. They published their findings in JCI Insight.

As Sarin explained in our release:

We discovered that people who develop six or more basal cell carcinomas during a 10-year period are about three times more likely than the general population to develop other, unrelated cancers. We’re hopeful that this finding could be a way to identify people at an increased risk for a life-threatening malignancy before those cancers develop.

Sarin and Cho wondered if this increased susceptibility could be due to errors in the biological pathways that exist to repair not only sun-caused DNA damage, but also other genetic missteps that can lead to cancer. Their hunch turned out to be correct.

More from our release:

Sarin and Cho studied 61 people treated at Stanford Health Care for unusually frequent basal cell carcinomas — an average of 11 per patient over a 10-year period. They investigated whether these people may have mutations in 29 genes that code for DNA-damage-repair proteins.

'We found that about 20 percent of the people with frequent basal cell carcinomas have a mutation in one of the genes responsible for repairing DNA damage, versus about 3 percent of the general population. That’s shockingly high,' Sarin said.

The researchers confirmed their findings in a larger group of patients in a database of medical insurance claims. They found that the more than 13,000 people with frequent basal cell carcinomas were also three times more likely than their peers to have other types of cancers, including breast, colon, melanoma and blood cancers.

Despite the results, the researchers emphasize that an occasional basal cell carcinoma doesn't mean you're likely to develop other cancers. (Of course, it's still important to know the signs of skin cancer and call your doctor if anything seems amiss.)

"I was surprised to see such a strong correlation," Sarin told me. "But it’s also very gratifying. Now we can ask patients with repeated basal cell carcinomas whether they have family members with other types of cancers, and perhaps suggest that they consider genetic testing and increased screening."

Photo by Vasiliki Theodoridou

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