Five Is Magic Number for Preventing Breast Cancer Recurrence
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"Prior to the alert, I think people were commonly put on open-ended therapy," Marilyn Leitch, MD, professor of surgery at the University of Texas Southwestern Medical Center at Dallas, tells WebMD. "The idea was that if five years of therapy was better than two years, more than five years must be even better. That is what we were hoping, but it doesn't appear to be the case."
Tamoxifen works against breast cancers by blocking the effects of the estrogen that spurs their growth. In addition to preventing breast cancer recurrences, the drug is also being used to prevent first cancers in women at increased risk for the disease. Patients on tamoxifen may experience certain menopausal symptoms like hot flashes, and a small percentage of women taking the drug develop blood clots. On the positive side, tamoxifen therapy has been shown to slow the bone loss commonly seen with aging, and help lower cholesterol.
In addition to the NSABP data, another large study from Scotland also found five years of postsurgical tamoxifen therapy to be optimal in most breast cancer patients. But the questions surrounding duration of therapy may not be resolved until two large British trials are reported a decade from now.
"It really does boil down to opinion at this point, but the totality of the evidence that we have available to date argues against more than five years of tamoxifen therapy," says Bryant, who is director of the NCI's NSABP Biostatistical Center. "In 10 years we may have conclusive answers, but by then we are likely to have better agents that are like tamoxifen, but don't have the side effects."