Oral bisphosphonates and breast cancer risk: results from two studies published in JCO

June 23, 2010

Results from two studies published online in the Journal of Clinical Oncology both suggest that the use of oral bisphosphonates, drugs used to treat osteoporosis, may inhibit the development of breast cancer. 

In one study, the association between oral bisphosphonate use and invasive breast cancer was examined in postmenopausal women enrolled in the Women's Health Initiative (WHI) study.  Of the 154,768 participants in the study, 2,816 were oral bisphosphonate users at entry.  After 7.8 mean years of follow-up, invasive breast cancer incidence was significantly lower in bisphosphonate users, though the incidence of DCIS was significantly higher. 

In the Breast Cancer in Northern Israel Study, the prior use of bisphosphonates was assessed in 4,039 postmenopausal breast cancer patients and controls, using pharmacy records.  The use of bisphosphonates for longer than one year before diagnosis was associated with a significantly reduced relative risk of breast cancer.  The association remained significant after adjustment for age, fruit, and vegetable consumption, sports activity, family history of breast cancer, ethnic group, body mass index, use of calcium supplements, hormone replacement therapy use, number of pregnancies, months of breast feeding, and age at first pregnancy.  Also, the breast tumors in bisphosphonates users were more likely to be estrogen receptor-positive and less often poorly differentiated.