Mixed Results Found in Study of Vitamins’ Effects on Cancer : Research: They helped prevent certain oral tumors but had no effect on the recurrence of skin cancers.

A promising approach to preventing cancer with the help of vitamins and other nutrients has produced mixed results in two new studies: They found that two forms of Vitamin A helped prevent certain oral tumors but had no effect on the recurrence of skin cancers.

The studies, reported today in The New England Journal of Medicine, are among the first to explore so-called chemo-prevention--the use of nutrients and drugs to try to delay the development of lung, colon, breast and other cancers.

The experimental approach is based on the observation that people who eat diets high in certain nutrients have relatively low cancer rates. Researchers nationwide are now conducting dozens of trials to explore whether such nutrients might therefore prevent cancer.

“If even a few provide positive results, the manner in which we view the management of cancer is likely to undergo a fundamental change,” wrote Dr. Frank L. Meyskens Jr. of the UC Irvine Clinical Cancer Center in an editorial accompanying the studies.

One of the two studies involved patients who had been successfully treated for cancers of the larynx, pharynx and oral cavity, but who still faced a substantial risk of recurrence. About 43,000 Americans develop such cancers each year; about 12,000 die of those cancers.

For one year, about half the 103 patients were assigned to take isotretinoin, a synthetic version of Vitamin A also used to treat severe acne. The other patients, believed to be comparable to the first group, received an inert placebo.

Following up the patients an average of 32 months later, the researchers found that two patients, or 4%, of those who received isotretinoin had developed second tumors. Twelve patients, or 24%, of the other group had new tumors and some had multiple tumors.

The drug did, however, have serious side-effects, including skin dryness, conjunctivitis and an increase in fats in the blood.

The drug did not affect the recurrence of the original tumors.

The other study involved patients who had had a previous case of so-called basal-cell or squamous-cell cancer, two common forms of skin cancer. Like people with a previous head-and-neck cancer, such patients are at high risk of developing another skin cancer.

About half of the 1,805 patients in the skin-cancer study were assigned to take daily doses of beta carotene, a chemical that becomes Vitamin A in the body. Beta carotene is found in a wide range of vegetables and fruits from carrots to cantaloupe.

After five years, the researchers found no difference between the two groups in the occurrence of new skin cancers--362 patients who took beta carotene and 340 of the others developed at least one new skin cancer.

“So I think we can conclude that over this period of treatment and observations, beta carotene had no effect in human skin cancer,” said Dr. E. Robert Greenberg, a professor of community and family medicine at Dartmouth Medical School and an author of the study.

“And that, I think, at least puts to rest the idea that beta carotene could serve as a cancer preventive agent that might be effective late in the process of cancer occurrence,” Greenberg said.

Greenberg and others said it remains possible that beta carotene might prevent other types of cancer, or that it might be effective when given earlier in the cancer-development process than it was in his study.

Greenberg’s study was conducted at Dartmouth, UCLA, UC San Francisco and the University of Minnesota. The isotretinoin study was headed by researchers at the University of Texas, M.D. Anderson Cancer Center in Houston.