Osteoporosis Medications Not Shown to Protect Against Breast Cancer
New analysis including research by Dr. Steven Cummings and colleagues of clinical trial data finds earlier evidence was misleading
August 11, 2014
According to new research by Steven Cummings, M.D., and colleagues, bisphosphonates (common osteoporosis drugs) may not protect women from breast cancer, contrary to earlier evidence from observational studies.
The findings were published August 11 in JAMA Internal Medicine.
The researchers assessed the effect of two of the most widely used osteoporosis drugs – alendronate and zoledronic acid – in randomized clinical trials, and neither drug protected women with osteoporosis from developing breast cancer. Low estrogen was noted as contributing to the decreased risk of cancer found in the previous observational studies, instead.
Since having low estrogen both weakens bones and protects against most breast cancers, the women most likely to be prescribed drugs for osteoporosis are usually also at lower risk for breast cancer, according to lead author Trisha Hue, PhD, an epidemiologist at the San Francisco Coordinating Center (SFCC) and the University of California, San Francisco.
“They may have seen a lower risk of breast cancer in women using bisphosphonates in the earlier observational studies because those women had a lower risk of breast cancer to begin with,” said Dr. Hue. “Postmenopausal women with osteoporosis usually have low estrogen levels. Lower levels of estrogen are strongly associated with a lower risk of breast cancer.”
Steven Cummings, MD, co-author of the paper, Senior Scientist at California Pacific Medical Center, and Director of the SFCC, added that “Post-menopausal women should continue taking these drugs for the prevention of fractures, but they should not use bisphosphonates for the prevention of primary breast cancer.”
Other centers involved in the study included the University of Pittsburgh, University of Minnesota, and University of California, San Diego.
The clinical trials analyzed in the study were the Fracture Intervention Trial (FIT) and the Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly-Pivotal Fracture Trial (HORIZON-PFT).