Older women at higher risk for breast cancer now have two good drug options for preventing the disease, but they will have to weigh the trade-offs, a major study shows.
Tamoxifen, the longtime gold standard, is more effective and longer lasting, the results show. But a newer drug – raloxifene, sold as Evista – is safer.
“I don’t see a clear winner,” but two good choices with different risks and benefits, said Dr. Scott Lippman, a cancer specialist at the University of Texas M. D. Anderson Cancer Center.
He is editor of Cancer Prevention Research, a journal that published long-term results from the federally funded study on Monday.
Tamoxifen is widely used to treat cancer once it’s diagnosed, and Evista is used to treat osteoporosis. But the drugs have not found wide acceptance so far as cancer preventives. Doctors hope the findings will spur more high-risk women to consider taking one of the drugs.
Tamoxifen cut the chances of developing the most serious forms of breast cancer in half, the research shows, but with a higher risk of uterine cancer. Evista cut the cancer risk by 38 percent, with fewer uterine problems and other serious side effects.
“We’ve now documented that it’s far less toxic” than tamoxifen, said study leader Dr. D. Lawrence Wickerham. He is a cancer specialist at Allegheny General Hospital in Pittsburgh who has consulted for makers of both drugs.
Tamoxifen has long been used to treat and prevent breast cancer. It blunts estrogen, which fuels the growth of most tumors that occur after menopause.
Evista, sold by Indianapolis-based Eli Lilly & Co., more selectively blocks estrogen. It is only for use after menopause; its safety and effectiveness before then are unknown.
Generic tamoxifen costs about 30 cents a day, versus up to $3 for Evista.
The study, called STAR, compared them in nearly 20,000 postmenopausal women at higher risk of breast cancer. They took one drug or the other for about five years and then stopped (longer use is not known to be safe or good).
After about seven years of follow-up, there were 310 cases of invasive breast cancer among women on Evista versus 247 in those on tamoxifen. That works out to a 24 percent higher cancer rate for Evista users.
Uterine cancer developed in 65 tamoxifen users but in only 37 women on Evista. Twice as many women on tamoxifen had abnormal uterine growths that led to hysterectomies. Blood clots and cataracts also were less common with Evista.