Researchers from the University of Michigan have reported that women at high-risk of breast cancer understand the risks and benefits of tamoxifen [Nolvadex®] prevention, but only 6% choose to take it. The details of this study were published in an early online publication in Breast Cancer Research on November 12, 2009.
Several large clinical trials have shown that tamoxifen can decrease the risk of breast cancer in high-risk women. There are, however, two issues that have prevented widespread use of tamoxifen for breast cancer prevention:
* Who is at risk? The definition of who is high risk is problematic and differs from trial to trial. Generally, high risk includes women with a family history of breast cancer, early menarche, later or no childbirth, or previous breast biopsy, even if negative.
* What are the side effects? In one study, it was found that less than one in five women at high risk would take tamoxifen due to their fears of side effects and the fact that they assumed they were at relatively low risk for developing breast cancer.
Two reports in the February 21, 2007 issue of the Journal of the National Cancer Institute document that tamoxifen can prevent hormone-positive breast cancer in women at high risk.
Researchers affiliated with the Royal Marsden Randomized, Double-Blinded Tamoxifen Breast Cancer Prevention Trial reported 20-year follow-up data. This trial randomly allocated 2,494 women at high risk of developing breast cancer to receive tamoxifen or placebo for eight years. A total of 82 women in the tamoxifen group and 104 in the placebo group developed invasive breast cancer. Researchers affiliated with the first International Breast Cancer Intervention Study (IBIS-I) reported that the breast cancer preventative effects of tamoxifen persist for at least 10 years after a five-year treatment period. This trial randomly allocated 7,145 women at increased risk for developing breast cancer to receive five years of tamoxifen or placebo. With a 96-month follow-up, there were 142 breast cancers in the tamoxifen group and 195 in the placebo group. They observed a preventive effect during the entire period of observation. The main side effects were an increased risk of deep-vein thrombosis and pulmonary embolism during but not after tamoxifen treatment. The estimated risk for developing estrogen receptor-positive breast cancer was 34% lower in the tamoxifen group.
The authors of the present trial sought to determine why few women with increased risk of breast cancer use tamoxifen for chemoprevention. They evaluated 632 women with an average 2.56% risk of developing breast cancer within five years. These women were presented with a tailored decision aid concerning the effectiveness of chemoprevention with tamoxifen and the known side effects. After reviewing the decision aid, 29% of women said they would seek more information from their own physician, and 6% said they would agree to take tamoxifen. These researchers thought that these women had adequate knowledge to make a decision. The stated: “Participants were concerned about the risks of tamoxifen, and many believed that the benefits of tamoxifen did not outweigh the risks.”
Discovering Key to Tamoxifen’s Effectiveness in Treating Breast Cancer may Mean New Treatments
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