A common class of bone-strengthening osteoporosis drugs, known as bisphosphonates, may significantly reduce the risk of breast cancer, according to an analysis of data from the Women's Health Initiative (WHI). The analysis was presented at the San Antonio Breast Cancer Symposium in December 2009.

The WHI data included information on more than 150,000 post-menopausal women, all of whom were generally healthy. Of the total study group, 2,816 were being treated with oral bisphosphonates. And of that small sector of participants, only 64 developed breast cancer. The researchers found that the women who were taking bisphosphonates had 32% fewer cases of invasive breast cancer than the women who were not being treated with the class of osteoporosis drugs.

There are approximately 30 million prescriptions for bisphosphonates written annually in the United States alone, according to Dr. Rowan Chlebowski, the study's lead researcher.

How Bisphosphonates Work
Bisphosphonates increase your bone mineral density by slowing down the rate at which your bone-absorbing osteoclasts work. Therefore, they help prevent fractures, including spinal compression fractures.

The bisphosphonates below are approved to prevent and/or treat osteoporosis:

• Alendronate (marketed as Fosamax): It is ideal if your osteoporosis was caused by excessive usage of steroid medications. It increases your bone mass to protect against fractures. This medication is taken orally.
• Ibandronate (Boniva): It specifically helps lower your risk of a spinal fracture. This medication is taken orally or intravenously.
• Risedronate (Actonel): Like alendronate, it is a good medication if overuse of steroid medications caused your osteoporosis. But risedronate also prevents against steroid-induced osteoporosis. This medication is taken orally.
• Zoledronic acid (Reclast): It increases your bone mass to protect against fractures. This medication is taken intravenously.

To learn more, read our article about drugs and medications for osteoporosis.

The Bisphosphonate-Breast Cancer Connection
The association between bisphosphonates and breast cancer began with a clinical trial in 2008 that found that patients with breast cancer who were given bisphosphonate treatment intravenously every 6 months had fewer cases of new cancers developing in the other breast.

This analysis of WHI data, on the other hand, focused on bolstering the limited research available for oral bisphosphonate's influence on breast cancer.

From the findings, the researchers concluded that oral bisphosphonates may be directly involved in preventing breast cancer.

To learn more about this study, read the abstract here.