New breast cancer drug as effective as tamoxifen
CTV.ca News Staff
Striking new results of an international breast cancer study show that the drug raloxifene is as effective as tamoxifen in the prevention of the disease in older, high-risk women.
The four-year study, sponsored by the U.S. National Cancer Institute (NCI), involved 19,474 post-menopausal women around the world -- all at increased risk of breast cancer -- and is being hailed as a significant step forward in preventing the disease.
Initial research found that the osteoporosis drug raloxifene was just as effective as the most commonly-prescribed preventative cancer treatment tamoxifen -- with fewer side effects.
Raloxifene reduces a woman's chances of developing breast cancer by 50 per cent, just like tamoxifen, but without the same side effects, the study says.
"This optimistic news is a significant step in breast cancer prevention," said John E. Niederhuber, of the NCI.
The Study of Tamoxifen and Raloxifene (STAR) is the largest clinical trial ever carried out on women at risk of developing breast cancer.
"It's a big study for us in the field of cancer prevention because it shows that a drug which is known to be safe . . . can really reduce the risk of breast cancer among women at risk," Dr. Michael Pollak, director of McGill University's cancer prevention division, told CTV Newsnet on Monday.
The study found that compared to women who were assigned to take tamoxifen, those who were prospectively and randomly assigned to take raloxifene daily, and who were followed for an average of about four years, had:
36 per cent fewer uterine cancers; and
29 per cent fewer blood clots.
Until now, tamoxifen has been the only drug approved to reduce the chances of breast cancer in women deemed "high-risk."
Previous studies had suggested raloxifene, sold under the brand name Evista by Eli Lilly & Co., could also prevent breast cancer in some women, although it was not approved for that use.
Both drugs are "selective estrogen response modulators." They act like the estrogen hormone in some tissues but like an anti-estrogen in others.
Side effects
Estrogen is known to fuel certain breast cancers, making tamoxifen a longtime choice in preventing the disease's return in women with estrogen-sensitive tumors; and to reduce the odds of it striking high-risk women in the first place.
But tamoxifen can cause serious side-effects as uterine cancer (except in women who have had hysterectomies), blood clots in the legs or lungs, and stroke.
Raloxifene can cause the same side effects, but not as many.
While the threat of stroke was about equal for both drugs, the incidence of uterine cancer was:
38 per cent lower with raloxifene than tamoxifen;
36 per cent lower for potentially life-threatening blood clots to the lungs; and
26 per cent lower for leg clots (deep vein thrombosis).
There are also indications that raloxifene, unlike tamoxifen, does not raise a woman's risk of developing a cataract.
What this means for patients
Researchers stress that the new study does not mean a change for pre-menopausal women with a high risk of breast cancer -- as there is no data showing whether raloxifene is safe for that group.
Pollak said those who believe they are candidates for the drug still need to consult their physicians.
"I personally think that, initially, the usage of (raloxifene) as a result of the results reported today, will be with women who already know that they have some elevated risk," Pollack told CTV Newsnet.
"Perhaps they have had a biopsy of their breast for a lump which was not cancerous but was precancerous, and there was some concern they might be at increased risk. That sort of woman probably would be the first subset of women who would be motivated to take this agent for the purposes of prevention."
Pollack adds that breast cancer remains to be a "huge problem" for women, and controlling growing rates of the disease will involve improving not just treatment, but prevention.
"There are some diseases that are controlled completely by prevention when we never were able to treat them. The best example is polio," said Pollack.
"Polio is controlled because we prevent it. We really cannot treat it very well. Now, breast cancer is not like that. To grapple with breast cancer in the Western world we are going to have to get better at prevention and better at treatment, because prevention will never be foolproof, in my opinion, but this study is a step forward . . ."
Pollack pointed to the danger, however, of giving into the mindset that breast cancer prevention "is only a question of drugs."
"We're also of course interested in promoting healthy lifestyles --eating well and doing all the other things that are important for minimizing risk."
Toronto's Women's College Hospital was also involved in the research and had 167 women included as part of the study. It's the second cancer prevention trial that Women's College Hospital has been involved in with the NCI.
"Breast cancer is the cancer most feared by women," said Dr. Lavina Lickley, the principal investigator leading the Toronto collaboration and a specialist in breast problems at Women's College Hospital.
"Efforts to find cures and methods of prevention are absolutely essential and we were very proud to take part in this breast cancer study," added Lickley.
"The real heroes in this study are the women who took part in it."
Research was conducted in collaboration with Toronto's North York General Hospital, Sunnybrook Hospital and the University Health Network.
Women who participated in STAR were postmenopausal, at least 35 years old, and had an increased risk of breast cancer as determined by their age, family history of breast cancer, personal medical history, age at first menstrual period, and age at first live birth.
STAR investigators will present additional data from the study in Atlanta, Ga. between June 2 and June 6 at the 42nd annual meeting of the American Society for Clinical Oncology.
jorja
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