An antiparasitic drug used to treat African sleeping sickness appears to offer protection against nonmelanoma skin cancers for years after the drug is taken, researchers say.

A study unveiled at a cancer prevention conference this week in Boston investigated the prolonged effect of the drug ?-difluoromethylornithine (DFMO) on 209 people with a history of nonmelanoma skin cancers.

Researchers found that the protective effect of the sleeping sickness medication against skin cancer continued for years, according to Dr. Howard H. Bailey of the University of Wisconsin School of Medicine and Public Health

More studies are needed, researchers caution, but the advance is a welcome one.

"The incidence [of nonmelanoma skin cancer] continues to rise despite public health efforts to get people to lessen their sun exposure," Dr. Bailey said, noting that there are more than 2 million cases of nonmelanoma skin cancer diagnosed each year in the U.S.