Cancer Shield

Could there be a pill to prevent cancer? Since the 1970s, experiments with lab animals and studies of cancer rates in different countries have suggested that certain vitamins or related compounds could at least lower the risk of getting some forms of the disease. That evidence has prompted a series of large trials in humans to see if these substances can throw a shield around potential cancer victims.

Last week brought the first modest success story in this new field of "chemo-prevention." Dr. Waun Ki Hong and colleagues from the University of Texas in Houston reported evidence that some cancers can be thwarted by isotretinoin, a man-made derivative of vitamin A that is sold as an anti-acne medication under the brand name Accutane. Fifty patients who had been successfully treated for cancer of the mouth and throat were given large daily doses of the drug for 12 months. After as much as three years, only two (4%) of the subjects developed a new cancer. In contrast, among 50 patients who received a placebo, 12 (24%) were stricken by a second tumor.

Doctors point out that isotretinoin is hardly a benign drug. In addition to causing side effects ranging from dry, scaly skin to high levels of fat in the bloodstream, the drug is believed to have triggered hundreds of birth defects when it was taken by pregnant women during the early 1980s.

Scientists do not expect to find a single chemical that can prevent all types of cancer. But they hope to discover a variety of compounds that could be useful for people who, because of their heredity or life-style, are known to be highly susceptible to particular kinds of malignancy. About 20 different cancer-prevention studies are under way around the world, examining the potential benefits of such compounds as beta carotene and vitamin A.