Benign Breast Disease and Breast Cancer Risk: Potential Role for Antiestrogens¹

Evidence from clinical follow-up studies has indicated that there is a relationship between the presence of histologically proven benign breast disease and breast cancer risk, and that the risk varies according to the histological category of benign breast disease and hormonal status. The risk associated with these histological factors appears to be equal in both breasts, suggesting that these factors are best considered markers of generalized increased breast cancer risk rather than direct precursor lesions. A number of interesting observations gleaned from the Nashville Study, the Breast Cancer Detection Demonstration Project and the Nurses9 Health Study, among other studies, provide evidence of an interaction between these histological risk factors and estrogen in determining the level of breast cancer risk. In the National Surgical Adjuvant Breast Project P-1 trial, tamoxifen was associated with an 86% reduction in breast cancer risk among a small subset of women with biopsy-proven atypical hyperplasia. Taken together, these observations strongly suggest that there is an interaction between estrogen and histological factors in determining breast cancer risk, and that it may be possible to reduce the risk associated with these histological risk factors using antiestrogen therapy.