Prospects for the primary prevention of breast cancer.

In this paper, the rationale, stage of development, and known or potential adverse effects of three potential strategies for the prevention of breast cancer are reviewed. Two methods--the use of tamoxifen in postmenopausal women and the use of luteinizing hormone (LH)-releasing hormone agonists in premenopausal women--involve hormonal manipulation. In the premenopausal period, the goal is to reduce the number of ovulatory menstrual cycles a woman experiences in order to reduce her exposure to estrogen and progesterone. Physical activity during adolescence is proposed as a nonhormonal method of accomplishing this. The use of LH-releasing hormone agonists to produce a reversible menopause can also reduce a woman's cumulative exposure to ovarian steroid hormones. Tamoxifen, which is effective in breast cancer therapy, provides endocrine control of estrogen-regulated breast tumor growth. Breast cancer chemoprevention trials using tamoxifen among postmenopausal women have been proposed, and pilot studies are under way.