Task Force Considers Tamoxifen, Raloxifene to Prevent Breast Cancer

Laurie Barclay, MD

July 01, 2002

July 2, 2002 — Women should discuss the role of preventive therapy for breast cancer with their physicians, according to a report by the United States Preventive Services Task Force (USPSTF) in the July 2 issue of the Annals of Internal Medicine.

"We looked for randomized controlled trials of chemical prevention of breast cancer and found four in women without a previous diagnosis of that illness," lead author Linda S. Kinsinger, MD, MPH, from the University of North Carolina at Chapel Hill, says in a news release. "Three of the four involved tamoxifen and one involved raloxifene, which the [U.S. Food and Drug Administration] has not approved [for breast cancer]."

Review of these major studies suggests that tamoxifen reduced the relative risk by nearly 50% and raloxifene by 76% for women at increased risk because of family history, early menarche, later or no childbirth, or previous breast biopsy, even if negative. Tamoxifen and raloxifene were effective only against estrogen receptor-positive tumors.

The largest tamoxifen study, involving more than 13,000 U.S. women with an estimated five-year breast cancer risk of at least 1.66%, showed a 49% risk reduction (relative risk, 0.51; 95% confidence interval [CI], 0.39-0.66). However, the two smaller tamoxifen studies conducted in Europe showed no statistically significant benefit.

"Only a few women in each of those trials took tamoxifen during the entire study period, and so that might be the reason there was no observed benefit," Kinsinger said. "Other possible reasons were that the studies were small and shorter-term."

The raloxifene study of postmenopausal women with osteoporosis found a 76% reduction in relative risk (0.24; CI, 0.13-0.44) for invasive breast cancer.

"These are pretty substantial effects and are worth considering," Kinsinger said. "Unfortunately, the two drugs can have side effects, including some that are potentially serious. That creates something of a dilemma for patients and doctors when it comes to decision-making." The USPSTF also reviewed cost-effectiveness and risk-benefit analysis of drug treatment to prevent breast cancer. Contraindications to preventive therapy include history of thrombosis, hypertension, or diabetes. Both drugs increased the risk of venous thromboembolic disease and hot flashes, and tamoxifen slightly increased the risk of endometrial cancer and stroke.

"It would be nice if we could say clearly that certain women should take one or the other of these drugs and that certain other women should not take them. Unfortunately, life's usually not as simple as that," Kinsinger said. "Women should discuss this with their doctors and come to a decision together."

In 2006, the decision may become a little easier. Results from the National Cancer Institute's Study of Tamoxifen and Raloxifene (STAR) trial, which directly compares tamoxifen and raloxifene, are expected to be available.

Ann Intern Med. 2002;137(13):000-000

Reviewed by Gary D. Vogin, MD

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