Basal cell carcinoma may increase risk for the development of other cancers, including blood, breast, colon and prostate cancers, according to a preliminary study by researchers at the Stanford University School of Medicine.

"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," says Kavita Sarin, MD, PhD, assistant professor of dermatology, in a news release. "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."

Dr, Sarin is the senior author of the study, which appears online in JCI Insight. Medical student Hyunje Cho is the lead author.

Drs 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," Dr. Sarin said.

Furthermore, 21 of the 61 people reported a history of additional cancers, including blood cancer, melanoma, prostate cancer, breast cancer and colon cancer -- a prevalence that suggests the frequent basal cell carcinoma patients are three times more likely than the general population to develop cancers.

'A strong correlation'

To confirm the findings, the researchers applied a similar analysis to a large medical insurance claims database. More than 13,000 people in the database had six or more basal cell carcinomas; these people also were over three times more likely to have developed other cancers, including colon, melanoma and blood cancers. Finally, the researchers identified an upward trend: the more basal cell carcinomas an individual reported, the more likely that person was to have had other cancers as well.

"I was surprised to see such a strong correlation," Dr. Sarin says. "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."

The researchers are continuing to enroll Stanford patients in the study, which is ongoing, to learn whether particular mutations in genes responsible for repairing DNA damage are linked to the development of specific malignancies. They'd also like to conduct a similar study in patients with frequent melanomas. But they emphasized that there's no reason for people with occasional basal cell carcinomas to worry.

"About 1 in 3 Caucasians will develop basal cell carcinoma at some point in their lifetime," Sarin says. "That doesn't mean that you have an increased risk of other cancers. If, however, you've been diagnosed with several basal cell carcinomas within a few years, you may want to speak with your doctor about whether you should undergo increased or more intensive cancer screening."