An inexpensive vitamin can help reduce the occurrence of common skin cancers in people prone to that disease, researchers reported on Wednesday.

In a clinical trial, people who took two pills a day of nicotinamide, a form of vitamin B3 available as a nutritional supplement, had a 23 percent lower risk of developing non-melanoma skin cancer than those who took placebo pills.

“It’s safe, it’s almost obscenely inexpensive and it’s widely available,” Dr. Diona Damian, the lead investigator of the study, said in a news conference organized by the American Society of Clinical Oncology, who said the findings could be put into practice right away.

“This one’s ready to go straight into the clinic,” said Dr. Damian, a dermatology professor at the University of Sydney in Australia. However, she said the vitamin should be used only by people who get frequent skin cancers, not by everyone.

The study will be presented at the annual meeting of the oncology society, which begins May 29 in Chicago. Abstracts for most of the nearly 5,000 studies were released late Wednesday, and a few results were discussed in a news conference organized by the society.

Investors and Wall Street analysts began poring over the abstracts late on Wednesday, looking for information that could affect the stocks of pharmaceutical companies.

In another study, an experimental drug for relapsed multiple myelomabeing developed by Bristol-Myers Squibb and AbbVie reduced the risk ofcancer progression by about 30 percent when added to two existing drugs.