A drug used to treat osteoporosis is as effective as tamoxifen in reducing breast cancer for postmenopausal women who are at increased risk of the disease. And it does so with fewer of the side effects associated with tamoxifen, according to preliminary results of a seven-year study.
Preliminary data from the multi-center "STAR Study" (the "Study of Tamoxifen and Raloxifene"), which included 83 Utah women who took part through the Huntsman Cancer Institute, was released Monday by the National Cancer Institute and the National Surgical Adjuvant Breast and Bowel Project, a network of cancer researchers.
The study found both drugs cut the risk of developing invasive breast cancer in half. But researchers found women who took raloxifene had 36 percent fewer uterine cancers (a very rare but serious side effect of tamoxifen) and 29 perfect fewer blood clots than those taking tamoxifen. Both drugs increase a woman's risk of blood clots compared to those who take neither drug.
"It's clear that we feel raloxifene has been the winner of this trial," Dr. D. Lawrence Wickerham, NSABP associate chairman and STAR protocol officer, said during a teleconference with reporters Monday afternoon.
"We think this gives women a real choice when addressing two of the leading causes of mortality and morbidity as they age — breast cancer and hip fracture," said Dr. Leslie Ford, associate director of clinical research at the NCI.
Prevention studies are extremely important, said oncologist Dr. John Ward, HCI principal investigator for the study and professor of medicine at the University of Utah. He treats women who have breast cancer and is committed to prevention as a better long-term strategy, he said.
This year, about 212,000 women, most of them past menopause, will be diagnosed with breast cancer. More than 40,000 will die of the disease. For the study, women were randomly assigned to receive one or the other of the two medicines, with a placebo version of the other to be sure that neither doctor nor patient could tell who was getting which drug.
Tamoxifen is marketed as Nolvadex, raloxifene as Evista. Tamoxifen has been used for 30 years to treat breast cancer patients. In 1998 it was approved as a prevention tool in high-risk, pre- and postmenopausal women. Raloxifene, also taken by pill, got FDA approval in 1997 to prevent osteoporosis in postmenopausal women but is not approved for use by women before menopause.
STAR followed 19,747 women for an average of four years. Participants had all completed menopause, were 35 or older and were at increased risk of breast cancer because of age, family breast cancer history, personal medical history, age of first menstrual period and age at first live birth. Women who are diabetic or had uncontrolled blood pressure were excluded from the study.
The number of women having strokes, heart disease and broken bones were similar for both groups. The two drugs are both known to protect bone health.
Raloxifene does not seem to increase the risk of developing a cataract, which tamoxifen does. And while both drugs have menopausal side effects like hot flashes, the incidence was lower with raloxifene.
Qualify of life was the same for both drugs. And an earlier study of tamoxifen found no increased risk of the drug's more serious side effects in women taking the drug under age 50.
Within hours of the preliminary data release, women in the study were being told which drug they'd been taking. Carolyn Burningham, a Bountiful woman whose daughter Marlynn, mother, sister and cousin all died of breast cancer, learned she has taken tamoxifen for the past four years.
Those who have not completed five full years of the medication were being given the option to continue until that time. There's no indication that women taking either drug receive additional benefit from taking it longer than five years, the study said. Those like Burningham who have been on tamoxifen can choose to switch to raloxifene if they'd rather.
Burningham has been participating in cancer studies at Huntsman for a decade now, she said.
"One of these days, they're going to announce they've put an end to (cancer)," she said.
This study is particularly important to her because she has so many relatives with breast cancer and she still has daughters and granddaughters who may battle it, as well.
"I've been very grateful to have a chance to try to make a difference," she said.
The findings of STAR do not automatically mean women should begin taking raloxifene, the researchers say. Women need to talk to their physicians about their specific indications for either medication. In some cases, tamoxifen may be a better choice. It cuts in half the incidence of a kind of precursor condition called lobular carcinoma in situ, which can turn malignant, while raloxifene has no effect on it, for instance.
"I think every intervention has a consequence," Ward said. "Even taking Evista will have a downside and it needs to be talked about in context with" a woman's individual situation.
Study medications and look-alike placebos were provided for free by the manufacturers, AtraZeneca Pharmaceuticals (tamoxifen) and Eli Lilly and Co. (raloxifene). The researchers plan to provide additional data when the American Society for Clinical Oncology meets in Atlanta in June.
E-mail: lois@desnews.com