The use of bisphosphonates for more than one year was associated with a 29 percent reduction in the risk of postmenopausal breast cancer, according to results presented at the annual CTRC-AACR San Antonio Breast Cancer Symposium, USA. 

Lead researcher Dr. Gad Rennert, chairman of the Department of Community Medicine and Epidemiology at the Carmel Medical Center of Clalit Health Services and a faculty member at the Technion-Israel Institute of Technology in Israel, said these data help shed light on a possible new pathway for breast cancer prevention.

"We have identified a new class of drugs that is associated with a reduced risk of breast cancer, and if proven in randomised trials, we may be able to recommend it to postmenopausal women for this purpose," said Rennert.

Rennert and colleagues extracted data from the Breast Cancer in Northern Israel Study, which is a population-based, case-control study. They evaluated the use of bisphosphonates for at least five years in 4,575 postmenopausal study participants using a structured interview.

The self-reported, long-term use of bisphosphonates prior to diagnosis was associated with a significant reduced relative risk for breast cancer by approximately 34 percent.

This reduction remained significant, at 29 percent, even after adjusting for a large variety of risk factors for breast cancer such as age, fruit and vegetable consumption, sports activity, family history of breast cancer, ethnic group, body mass index, calcium supplement and hormone replacement therapy use, number of pregnancies, months of breastfeeding and age at first pregnancy.

Moreover, the breast tumours identified among patients who used bisphosphonates were more often estrogen receptor positive and less often poorly differentiated.

"These tumours are the type that are associated with a better prognosis," said Rennert.