Two randomized clinical trials from the lab of Trisha F. Hue, Ph.D., M.P.H. at the University of California, San Francisco, have found that bisphosphonates aren’t likely to reduce a patient’s risk of breast cancer. The team found that three to four years of bisphosphonates, sometimes used to treat osteoporosis, is not linked to reduced risk of invasive postmenopausal breast cancer.
Stated in the press release: “The authors analyzed the relationship of postmenopausal breast cancer and bisphosphonate use by examining data from two randomized, double-blind, placebo-controlled trials. The Fracture Intervention Trial (FIT) randomly assigned 6, 459 women (ages 55 to 81 years) to alendronate or placebo with an average follow-up of 3.8 years. The Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly-Pivotal Fracture Trial (HORIZON-PFT) randomly assigned 7, 765 women (ages 65 to 89 years) to annual intravenous zoledronic acid or placebo with an average follow-up of 2.8 years. The authors compared rates of breast cancer in the bisphosphonate treatment groups to the placebo groups.”
According to the August 11, 2014 news release, there was no significant difference in breast cancer rates between the bisphosphonate and placebo groups. In FIT, the breast cancer rate was 1.5% in the placebo group and 1.8% in the alendronate group. In HORIZON-PFT the rate was 0.8% in the placebo group and 0.9% in the zoledronic acid group. There also was no significant difference when data from the two trials were combined.
“These data provide evidence that three to four years of treatment with bisphosphonate, alendronate or zoledronic acid, therapy does not reduce the risk of incident breast cancer in postmenopausal women. The discrepancy between our results and the reports of associations in observational studies may be an example of indication bias and illustrates the limitation and hazard of drawing conclusions about treatment effects from observational studies (even those that are very well done) and emphasizes the value of confirming such associations in randomized trials. The effect of bisphosphonate treatment on breast cancer risk in nonosteoporotic populations should be investigated in other randomized trials, ” wrote the authors.
