Raloxifene Lowers Breast Cancer Risk After Menopause
Reviewed study: "Raloxifene Lowers Breast Cancer Risk After Menopause" by S. Martino, et al., San Antonio Breast Cancer Symposium, December 2004, Abstract # 22
Background and importance of the study: Raloxifene (brand name: Evista) belongs to a family of drugs called SERMs (selective estrogen receptor modulators). In breast and certain other tissues, SERMs block the action of the hormone estrogen by sitting in the estrogen receptors on and within the cells. With the SERM in its place, estrogen can't attach to the breast cells and tell them to grow and divide.
But in other body tissues besides the breast, SERMs DO send estrogen-like signals. For example, SERMs seem to lower the risk of bone weakening in post-menopausal women by sending growth signals to bone cells. This is why raloxifene is given to post-menopausal women with the bone-thinning condition known as osteoporosis (as well as to women at risk of developing osteoporosis). Earlier studies have found that post-menopausal women who took raloxifene to treat osteoporosis had a much lower risk of breast cancer.
In July 2001, we reported on the results of the four-year Multiple Outcomes of Raloxifene Evaluation (MORE) study. In that large study, post-menopausal women with osteoporosis took raloxifene or a placebo (a "dummy" pill). Neither the women nor their doctors knew which pill they were taking.
The study found that raloxifene not only improved bone strength, but also significantly reduced the risk of breast cancer.
To see if this benefit held up over a longer time, researchers followed more than 7,000 of the women from the MORE study for another four years.
Study design: The researchers followed 4,843 women who had been taking raloxifene and 2,447 who had been taking a placebo over four years of the MORE study. Each group continued to take raloxifene or a placebo for four more years in this study, for a total of eight years.
At the end of the eight years, the researchers compared the rates of invasive breast cancer in the groups of women taking raloxifene and the placebo.
They also looked to see if the women's estrogen levels at the beginning of the study influenced the effectiveness of raloxifene. But all the women in the study were post-menopausal, so the difference in estrogen levels was rather small.
Study results: The researchers found that the women taking raloxifene had a 66% lower risk of developing invasive breast cancer compared to the women who took the placebo.
The researchers also found that the risk reducing effects of raloxifene were not affected by the levels of estrogen in the women's blood at the start of the study. Raloxifene reduced the risk of breast cancer in women with both higher and lower blood estrogen levels.
Another part of this study that we reported on in June 2004 found that raloxifene only lowered the risk of developing estrogen-receptor-positive breast cancers. It didn't seem to affect the risk of developing estrogen-receptor-negative breast cancer.
Conclusions: In this study, taking raloxifene for eight years significantly reduced the risk of developing invasive breast cancer in post-menopausal women with osteoporosis. This was true, no matter what the women's beginning blood estrogen levels were. Of note, these women did not have a personal history of breast cancer before participating in the study.
What breastcancer.org says about this article…
Raloxifene Lowers Breast Cancer Risk After Menopause
If you're post-menopausal and you already have osteoporosis or significant loss of bone strength, your doctor will probably recommend a medication to help you build up your bone strength. Raloxifene (otherwise known as "Evista") is an important treatment option to consider. It does offer the main benefit of helping you strengthen your bones. Plus, it also can reduce your risk of getting invasive breast cancer. (The kind of breast cancer it protects you against is hormone receptor positive disease.) This added benefit isn't seen with other osteoporosis drugs such as Fosamax (chemical name: alendronate sodium) and Actonel (chemical name: risedronate sodium). These other medicines are not SERMs but belong to a different category of drugs called bisphosphonates.But we don't know yet if raloxifene can lower the risk of breast cancer if you DON'T have osteoporosis or if you already have a personal history of breast cancer. Raloxifene has not been tested in pre-menopausal women, therefore it shouldn't be given to women before menopause.
If you think you might benefit from raloxifene, talk to your doctor. And stay tuned to Breastcancer.org for the results of additional studies that will shed more light on raloxifene and other SERMs. Visit our section on Bone Health to learn more about how to keep your bones healthy during breast cancer treatment and beyond.