Cancer chemoprevention

Encouraging results from several recent trials have increased interest in the potential of chemoprevention in reducing the incidence of cancer. Treatment with 13-cis-retinoic 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 preventing both the recurrence of breast cancer and the development of new tumors in the contralateral breast, and is being tested in high-risk patients who have not yet developed disease. The results of the Physicians' 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 carotene on the incidence of cancer still is underway. These studies demonstrate the importance of careful design if chemoprevention trials are to yield convincing data.