Breast Cancer Drugs Raloxifene and Tamoxifen Increase Blood Clot Risk

September 2009

Recent data have revealed that raloxifene and tamoxifen, drugs taken to reduce the risk of breast cancer, put women at a greater risk for serious health problems. Doctors and their patients are urged to weigh the drugs' benefits against their risks.

A new study found that women who took tamoxifen had a higher risk of cataracts and blood clots compared to those who took raloxifene. Patients who took tamoxifen also had twice the risk of endometrial cancer (uterine lining) as those who didn't take the drugs. Blood clots can lead to heart attacks and strokes, and endometrial cancer may require a hysterectomy.

Tamoxifen and raloxifene are selective estrogen-receptor modulators (SERMs), a class of drugs that reduces the risk of invasive breast cancer in at-risk women. For every 1,000 women who take the drugs each year, seven to 10 fewer cases of breast cancer will develop. For every 1,000 women who take tamoxifen each year, four to seven additional cases of blood clots occur.