(HealthDay News) — Data from two randomized controlled trials suggest that bisphosphonate use does not protect against postmenopausal breast cancer, according to research published online August 11 in JAMA Internal Medicine.

Trisha F. Hue, PhD, MPH, from the University of California in San Francisco, and colleagues examined the correlation between postmenopausal breast cancer incidence and bisphosphonate use. Data were obtained from the Fracture Intervention Trial (FIT), involving 6,459 women who were randomized to alendronate or placebo, and the Health Outcomes and Reduced Incidence With Zoledronic Acid Once Yearly-Pivotal Fracture Trial (HORIZON-PFT), involving 7,765 women, randomized to annual intravenous zoledronic acid or placebo. In both studies, the authors examined the hazard ratio for incident breast cancer in the bisphosphonate group versus the placebo group.

The researchers observed no significant between-group difference in the rate of breast cancer in FIT (1.5% in placebo group vs. 1.8% in alendronate group; hazard ratio [HR], 1.24; 95% confidence interval [CI], 0.84–1.83) or in HORIZON-PFT (0.8% in placebo group vs. 0.9% in zoledronic acid group; HR, 1.15; 95% CI, 0.70–1.89). When the data from FIT and HORIZON-PFT were pooled, there was no significant between-group difference noted (HR, 1.20; 95% CI, 0.89–1.63).

“Contrary to the results from observational studies, we found that three to four years of bisphosphonate treatment did not decrease the risk of invasive postmenopausal breast cancer,” the authors write.

One author disclosed financial ties to Merck Sharp & Dohme. FIT was funded by Merck and HORIZON-PFT was funded by Novartis.

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