Researchers found that after an average of 2.4 years of letrozole, 132 women taking the placebo, an inactive substance, developed a new breast cancer or a breast cancer recurrence, compared with 75 women who received letrozole. Researchers estimated that disease-free survival at four years would be 93 percent for women taking letrozole and 87 percent for the placebo group.
Women who received the letrozole therapy experienced low-grade hot flashes, arthritis and muscle pain more often than people not taking the therapy. Letrozole may also be associated with elevated cholesterol and osteoporosis, and ongoing studies are currently assessing those risks.
In addition to addressing safety issues, further research is needed to determine the optimal amount of time women should take the drug and if letrozole might be effective in women who have already stopped taking tamoxifen.
Treatment guidelines should available soon. For now, researchers say letrozole should be a consideration for women who have recently completed five years of tamoxifen. According to Dr. Gass, a variety of circumstances might make women good candidates. "Women who stopped taking tamoxifen a year ago, women who stopped taking it three years but are at high risk, or women who have serious side effects from tamoxifen should talk to their doctors about these results."
Coauthor Hyman Muss, MD, a professor of medicine at the University of Vermont and the Vermont Cancer Center, says women will have to weigh the risks and benefits. "These are exciting data, but five years after diagnosis, most women are going to do well," says Dr. Muss. "Letrozole is going to be more valuable to women with a somewhat higher risk for recurrence, such as those with more extensive lymph involvement or a larger tumor. It's got to be an individual decision."
