[Chemoprevention of breast cancer by tamoxifen: should we still ask this question?].

Pharmacoprevention of cancer is an attractive concept. For breast cancer, several trials were set up some years ago. The largest one was stopped before its planned date of closure and demonstrated an early appearing reduction in breast cancer occurrence; in contrast, the other two trials did not find such a protective effect. The decision is all the more difficult because of tamoxifen side effects, including carcinogenicity. Currently, no definite conclusion can be drawn.