(AP Photo/John Minchillo)

A cheap over-the-counter vitamin appears to reduce recurrence of some common skin cancers associated with sun exposure for people who have had them before, researchers reported Wednesday.

Nicotinamide, a form of vitamin B3, significantly reduced the number of new non-melanoma skin cancers among people who had suffered at least two such lesions in the previous five years, according to Australian researchers who conducted a year-long study of 386 people.

"It's safe, it's almost obscenely inexpensive and it's widely available," said Diona Damian, a professor of dermatology at the University of Sydney, who led the research team. "This one is ready to go into the clinic."

Damian emphasized that the research did not look at the general population, only people who had previously suffered skin diseases such as squamous cell carcinoma--which attacks the flat cells on the outer layer of the skin--and basal cell carcinoma, which affects the deepest part of the skin's outer layer. People who haven't been diagnosed with such cancers should not take nicotinamide preventively, she said.

However, Damian said the vitamin's protective quality should work for people in countries other than Australia where sunshine is less abundant.

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A summary of the results was released Wednesday and presented by Damian at a telephone news conference prior to the annual meeting of the American Society of Clinical Oncology, which is scheduled for later this month in Chicago.

Basal and squamous cell carcinomas are common cancers associated with sun exposure. Squamous cell cancer is often easily removed but can metastasize to other parts of the body and is occasionally fatal. Basal cell cancers are more common, with an estimated 2.8 million annually, according to the Skin Cancer Foundation. Nearly half of adults who live to age 65 will be diagnosed with at least one instance of such cancers.

The researchers put half the people in their study on 500 milligrams of nicotinamide twice a day and the other half on a placebo. The subjects, who averaged 66 years old, had an average of eight skin cancers each before the study, and one person had suffered 52.

The people who took the vitamin developed 1.77 new lesions over the next 12 months, while those on placebo developed 2.42, the results showed. When adjusted for other factors, the results were 23 percent better for people who took the vitamin, which also helped reduce the development of actinic keratoses, a non-cancerous scaly skin growth.

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Damian said the vitamin provides skin cells with a boost of energy and intensifies the rate of skin repair.

When the test subjects stopped taking the vitamin, the benefit was lost, a follow-up showed.

Damian said anyone who starts the preventive therapy must be careful not to take niacin, another form of vitamin B3 that can have side-effects. But overall, nicotinamide is an "affordable skin cancer prevention which we can instantly translate into clinical practice," she said.