Bone drugs linked to fewer cases of breast cancer
(21 December 2009: VIDYYA MEDICAL NEWS SERVICE) -- A new analysis from the Women’s Health Initiative (WHI) study has found that the use of drugs called bisphosphonates, which are taken to improve bone health, was associated with a nearly 33 percent reduction in the incidence of invasive breast cancer compared with women who did not take the drugs. Although preliminary, the findings raise the possibility that this commonly used class of drugs may have a role in preventing breast cancer, researchers said at the 2009 CTRC-AACR San Antonio Breast Cancer Symposium.
Bisphosphonates are taken primarily for the treatment of osteoporosis but can also treat bone-density problems in patients with cancer-related conditions. Laboratory studies have suggested that these agents may also have anticancer effects, providing a possible biological explanation for the association.
To find the association, Dr. Rowan Chlebowski of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center and his colleagues analyzed data on 151,000 women in the observational component of the WHI. Of the 2,216 women who were using bisphosphonates when they entered the study, 64 developed breast cancer, and most of those cancers (50) were estrogen-receptor positive.
The results translate into 32 percent fewer cases of invasive breast cancer among users of oral bisphosphonates—primarily alendronate (Fosamax)—compared with nonusers. A second study presented in San Antonio found a nearly 30 percent reduction of postmenopausal breast cancers among women in Israel who used bisphosphonates for at least a year compared with nonusers.
Since neither study was a randomized controlled trial, the results should be considered hypothesis-generating and are by no means proof, noted Dr. Leslie Ford of NCI’s Division of Cancer Prevention and the institute’s WHI liaison. “One issue is that women who take bisphosphonates often have low bone density because they are in a low estrogen environment,” she said, “so these women would be at a lower risk for breast cancer than women who did not get bisphosphonates.” This could be an alternative explanation for the result.
An ongoing clinical trial is looking at the role of bisphosphonates in the adjuvant treatment of breast cancer. If the results indicate that women taking the drugs have a lower rate of cancer in the opposite (contralateral) breast than women not taking bisphosphonates, this would “be a very intriguing finding and would make the current observations even stronger,” said Dr. Ford. Nonetheless, randomized controlled trials in the preventative setting would be needed for this to become the standard of care, she added.
Bisphosphonates have been linked to osteonecrosis of the jaw, and the FDA issued a warning about musculoskeletal side effects of these drugs in January 2008. A year later, the FDA’s Dr. Diane Wysowski warned of an increased risk of esophageal cancer and death in patients taking oral bisphosphonates.
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