WEDNESDAY, June 23 (HealthDay News) -- The use of oral bisphosphonates by postmenopausal women appears to significantly reduce the risk of some breast cancers, according to a pair of studies published online June 21 in the Journal of Clinical Oncology.
Rowan T. Chlebowski, M.D., of the Harbor-UCLA Medical Center in Torrance, Calif., and colleagues studied 154,768 postmenopausal women in the Women's Health Initiative, including 2,816 oral bisphosphonate users. After a mean follow-up of 7.8 years, invasive breast cancer and estrogen receptor-positive breast cancer incidence was lower in bisphosphonate users (hazard ratios, 0.68 and 0.70, respectively), however, the incidence of ductal carcinoma in situ was higher in bisphosphonate users (hazard ratio, 1.58).
In another study, Gad Rennert, M.D., of the Technion-Israel Institute of Technology in Haifa, and colleagues assessed the effect of bisphosphonate use on breast cancer risk in 4,039 postmenopausal women, including 1,832 breast cancer patients and a matched control group of 2,207 women. The researchers found that bisphosphonate use for longer than one year before diagnosis was associated with a significantly reduced breast cancer risk (odds ratio, 0.61) which remained significant after adjustment for diet, family history, and other factors (odds ratio, 0.72). The tumors in bisphosphonate users tended to be estrogen receptor-positive and less often poorly differentiated.
"The use of bisphosphonates for longer than one year was associated with a 28 percent relative reduction in the risk of postmenopausal breast cancer. Tumors developing under bisphosphonates treatment tended to have a favorable prognostic factors profile," Rennert and colleagues conclude.
The authors of the first study disclosed financial ties to several pharmaceutical companies.