THURSDAY, June 24 (HealthDay News) -- Bone-building drugs known as bisphosphonates appear to reduce the risk of invasive breast cancer by around 30 percent, two new studies show.
"If a woman is considering bisphosphonate use for bone, this might be another potential benefit," said Dr. Rowan T. Chlebowski, a clinical oncologist at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, Calif. He is the lead author of one of the two studies on the topic, published online this week in the Journal of Clinical Oncology.
The findings were first presented late last year at the San Antonio Breast Cancer Symposium, but Chlebowski said the results now have the benefit of having been peer-reviewed before publication for scientific accuracy.
Chlebowski and his colleagues looked at nearly 155,000 women who participated in the Women's Health Initiative (WHI) study, evaluating the 2,816 women who took oral bisphosphonates at the study start and comparing them to women who did not.
Ninety percent of the women who were taking the bone-building drugs took alendronate (Fosamax), according to the study.
After nearly eight years of follow-up, Chlebowski found invasive breast cancer incidence was 32 percent lower in those on bone-building drugs, with ER-positive cancers reduced by 30 percent. The incidence of ER-negative cancers in those on bisphosphonates also decreased, but not by enough to be statistically significant.
The incidence of early, noninvasive breast cancers, known as ductal carcinoma in situ, was 42 percent higher in bisphosphonate users, so the bisphosphonates could somehow be selectively affecting invasive cancers, Chlebowski postulated.
In a second study, conducted in Israel, researchers looked at 4,039 postmenopausal women, including some who took bisphosphonates and some who did not. Those who took the drug longer
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