Prevention of breast cancer using SERMs.

The development of breast cancer is dependant in part on oestrogen. Suppression of ovarian function or use of anti-oestrogens will reduce the incidence of breast cancer. Many trials have now been done involving tens of thousands of healthy women evaluating the use of selective oestrogen receptor modulators to reduce the risk of breast cancer in healthy women. Tamoxifen will reduce the early incidence of breast cancer in pre and postmenopausal women by about 40% but causes vasomotor symptoms, thromboembolism and gynaecological toxicity including polyps, endometrial atypia and rarely cancer. In long follow up trials the risk reduction for breast cancer extends beyond the treatment period out to at least 15 years appearing to get larger with time indicating a true long term prevention effect. The toxicity of tamoxifen is for the most part confined to the treatment period. Raloxifene also has similar breast cancer risk reduction activity to tamoxifen but has less toxicity with no evidence of an increased risk of endometrial atypia or cancer. Tamoxifen is licensed for breast cancer risk reduction in the USA and raloxifene has also recently been approved by the FDA for such use.