CANCER CHEMOPREVENTION

Encouraging results from several recent trials have increased interest in the potential of chemoprevention in reducing the incidence of canc er. Treatment with 13-cisretinoic acid has reversed oral leukoplakia, a premalignant lesion, and prevented the development of second primary carcinomas of the head and neck. Tamoxifen has proven effective in pr eventing both the recurrence of breast cancer and the development of n ew tumors in the contralateral breast, and is being tested in high-ris k patients who have not yet developed disease. The results of the Phys icians' Health Study, which demonstrated the effectiveness of aspirin in reducing heart attacks, already have been incorporated into health care practice, while the component investigating the effect of beta ca rotene on the incidence of cancer still is underway. These studies dem onstrate the importance of careful design if chemoprevention trials ar e to yield convincing data.