A new analysis reveals that tamoxifen reduces the incidence of breast cancer by 38 per cent in healthy women who are at high risk of the disease.

Scientists for the leading charity Cancer Research UK have been reviewing the evidence on tamoxifen's protective effects against breast cancer. The drug works by blocking the effects of estrogen and can help in those cancers which respond to estrogen exposure. In the current study, the effects of tamoxifen and a related drug, raloxifene, were reviewed in 14 trials covering over 40,000 women. This revealed an overall reduction of breast cancer risk of 38 per cent among women taking tamoxifen. For raloxifene, the reduction was as much as 64 per cent.

Some of the trials involved women who had already had cancer in one breast and were at risk of a recurrence in the other. Tamoxifen reduced the likelihood of this recurrence by 46 per cent. However, tamoxifen was also linked with some serious side effects - chiefly blood clotting and endometrial cancer. Ways must be found to reduce these. Raloxifene appears to be associated with fewer side effects and may, in future, be the drug of choice to protect against breast cancer. It could also be important to select women who are to have tamoxifen very carefully - perhaps excluding those felt to be most at risk from the drug's side effects.

Source

The Lancet 25th January 2003