Women with heart disease or a high risk for it would trade one set of odds for another if they took the drug raloxifene to try to prevent breast cancer, a new study suggests.
The drug helped prevent cancer, but raised the risk of blood clots and fatal strokes. It also didn’t lower the risk of death, hospitalization or heart attack, as some had hoped it would.
Doctors have been testing this drug as an alternative to tamoxifen for preventing breast cancer and as a way to lower heart disease risks.
Based on the new study’s results, “most people would decline taking raloxifene” unless they have a high risk of breast cancer, said Dr. Linda Vahdat, director of breast cancer research at Weill Cornell Medical College.
Dr. Marisa Weiss, a Philadelphia breast cancer specialist who founded the consumer Web site breastcancer.org, agreed.
“The cardiac benefit wasn’t there. The side effects were,” and breast cancer is more treatable than life-threatening blood clots and strokes, she said.
Neither doctor took part in the study, which involved 10,101 postmenopausal women in the United States and 25 other countries. Results were published in Thursday’s New England Journal of Medicine.
Many of the authors consult or work for Indianapolis-based Eli Lilly & Co., which makes raloxifene and paid for the study. The drug is sold as Evista for treating the bone disease osteoporosis, but the company is seeking approval to market it for breast cancer prevention.
A similar drug, tamoxifen, has long been used to prevent breast cancers whose growth is fueled by the hormone estrogen. A big federal study reported last month that raloxifene was equally effective at preventing the most serious types of breast cancer and with fewer side effects, although some doctors disagree on how large the differences in side effects really are.
That study, called STAR, directly compared the two drugs in women at higher-than-usual risk of developing breast cancer. The new study involved a different group of women — those at high risk of heart problems — and tested whether raloxifene was better than dummy pills at reducing breast cancer and heart-related risks.
Participants either had clogged arteries or multiple heart risk factors, such as advanced age, diabetes, smoking, high blood pressure or high cholesterol. About 40 percent also had elevated risk of breast cancer, mostly because of their age, but this was not the main reason they were in this study — their heart risk was.
Roughly half were given daily raloxifene pills and the others, dummy pills. Neither they nor their doctors knew who was taking what.
After an average of five years on the pills, deaths and major heart problems were about the same in both groups. Raloxifene users had one-third fewer cases of breast cancer and about half the number of invasive breast cancers — benefits seen previously.
However, 59 of the 5,044 raloxifene users had fatal strokes; only 39 of the 5,057 on dummy pills did, translating to a 49 percent greater risk for those taking the drug.
Blood clots in veins, which can be life-threatening if they travel to the lungs, formed in 103 women on raloxifene but only 71 of the others.
The “moderate” breast cancer prevention benefits “do not seem to justify the risks” of raloxifene for women already prone to heart problems, Marcia Stefanick, a disease prevention researcher at Stanford School of Medicine, wrote in an editorial in the medical journal.
However, the murky results make it important for women to talk about risks with their doctors, said Dr. Lori Mosca, one of the authors and director of preventive cardiology at New York Presbyterian Hospital in New York.
“Even though the study overall appears to be a wash, it’s important that every woman understand that the tipping point for her may be different. Every woman has a unique risk for breast cancer, for cardiovascular disease,” she said.
None of this changes tamoxifen’s status as the drug of choice for breast cancer prevention before menopause. Raloxifene’s safety and effectiveness in that situation is unknown.