Women being treated for primary breast cancer may be given tamoxifen before surgery to shrink the tumour or afterwards to mop up any cancer cells left behind. And tamoxifen is commonly given to women with secondary breast cancer to halt the growth of cancer cells.
Compared with other drugs used to treat breast cancer, tamoxifen is virtually non toxic - but it gets results. Women who take tamoxifen as adjuvant therapy for early stage breast cancer are only half as likely to develop the disease in the opposite breast as those who do not take it and it reduces breast cancer recurrence by a third.
Taken as a daily tablet, it prevents oestrogen being taken up by receptors in the cancer cells. This slows or stops the spread of cancer. Now researchers want to find out if tamoxifen can prevent the disease: trials are already underway but more volunteers - women believed to be at a higher than normal risk of breast cancer - are being invited to take part in the International Breast Cancer Intervention Study (IBIS).
The trouble is that tamoxifen is not without risks of its own. These risks may be small but include the possibility of developing endometrial cancer, eye damage and blood clots. Rats given tamoxifen in huge doses develop liver cancer.
But for most women who have already been diagnosed with breast cancer, the benefits of taking tamoxifen far outweigh these risks.
But the debate still rages as to whether healthy women should be taking tamoxifen. "It's up to every woman to have the opportunity to participate in the study if she wishes," says study co-ordinator Clare O'Neil. "But this can only be done if she has access to full information from breast cancer specialists.
"Women who come forward have been living with the fear of breast cancer hanging over them, affecting every day of their lives. In some small way, participating in the study can help alleviate some of their anxiety."
Research into the best use of tamoxifen for women who already have breast cancer is also progressing. Trials are now underway to help specialists investigate the optimum time that women with breast cancer should be treated with the drug.
*If you have a family history of breast cancer and would like to take part in IBIS, write to Clare O'Neil, study co-ordinator, PO Box 123, London WC2A 3PX.Reuse content