Breast Cancer, Aromatase Inhibitors, and Bone Density

Aromatase inhibitors (AIs), such as Arimidex, Aromasin, and Femara, have proven to be more effective than previous hormonal treatments for treating both early and advanced breast cancer in post-menopausal women whose tumors are dependent on estrogen. Compared with tamoxifen, these drugs are less likely to cause blood clots or raise the risk of endometrial cancer. As a result, AIs are used both in patients with early breast cancer and in those with metastatic disease.

The downside is that AIs increase the risk of osteoporosis (severe thinning of the bones) and bone fractures.

If you are taking an AI, you should:

  • Have a bone mineral density test when you begin taking the drug.
  • Make sure your bone density continues to be checked regularly during AI treatment

If the tests reveal osteoporosis, you can reduce the risk of suffering a fracture by appropriate treatment with calcium and vitamin D supplements, and bone-strengthening drugs called bisphosphonates.

Jennifer Ligibel, MD

A recent report led by Jennifer Ligibel, MD, a breast oncologist in the Susan Smith Center for Women’s Cancers at Dana-Farber, looked at records of more than 9,000 women who took AIs between 2002 and 2008. The new study was the first to measure the rates of bone-density testing in this population.

  • Only 41.6 percent of patients received bone density testing when starting the therapy.
  • In the subset of women who took aromatase inhibitors for at least two years, just 59.9 percent underwent testing during their first two years on the drugs.

“If these patterns continue,” the report warns, “many women who are cured of their early-stage breast cancers could develop bone loss and fractures as a result of their cancer therapy.”

These statistics are worrisome, says Ligibel. “There needs to be more awareness that if you’re on an aromatase inhibitor, you should have your bone density checked with some degree of regularity.”