Dec. 5, 2012 -- Doubling the time that breast cancer patients take tamoxifen cuts the risk that the cancer will come back and further lowers the risk of dying of the disease, a new study shows.
The study is expected to change the way doctors prescribe tamoxifen, a drug that blocks the effects of estrogen on breast cells. About 80% of all breast cancers are sensitive to the hormone estrogen for growth.
The research also hints that longer courses of other kinds of hormone-reducing medications may also work better than shorter courses after breast cancer surgery, though trials testing that theory are ongoing.
“I think the result of this trial will have a major immediate impact on premenopausal women,” says Peter Ravdin, MD, PhD. Ravdin is the director of the Breast Health Clinic at the Cancer Therapy and Research Center at the University of Texas Health Science Center, in San Antonio.
Newer kinds of estrogen-reducing drugs, called aromatase inhibitors, have largely replaced tamoxifen as the preferred therapy for postmenopausal women with estrogen-sensitive cancers. This study won’t change that.
But those kinds of drugs don’t work for women before menopause. For them, doctors still recommend taking tamoxifen.
Current guidelines recommend that women stop tamoxifen after five years because the drug increases the risk of uterine cancers and dangerous blood clots.
The new study found small increases in cases of uterine cancer in women who took the drug for an additional five years. Those women also had slightly higher risks of developing a blood clot in their lungs. But those additional risks did not appear to outweigh the survival benefits of staying on the drug.
“I think that for women who are now approaching five years of therapy, where we’d usually be telling them -- up to this point -- that we’re going to be stopping the tamoxifen, now we’re going to be telling them that there is clinical evidence that 10 years is superior to five years, and I’m going to be comfortable doing that,” says Ravdin, who led a news briefing on the study but was not involved in the research.
The study was published in the Lancet and presented to doctors at the 2012 San Antonio Breast Cancer Symposium.