Breast cancer experts release guidelines on use of aromatase inhibitors

More than 100,000 women each year are diagnosed with a type of breast cancer called postmenopausal estrogen receptor-positive -- the most common type of breast cancer. Studies in recent years have shown that an important tool to prevent recurrence of this type of breast cancer lies in the use of medications called aromatase inhibitors.

On Monday, cancer experts issued guidelines updating the knowledge about aromatase inhibitors -- which are medications that lower estrogen -- and how women and their doctors should best utilize this class of drugs. The guidelines, released by the American Society of Clinical Oncology, are published in the Journal of Clinical Oncology.

The guidelines urge all post-menopausal women with this type of breast cancer to use an aromatase inhibitor either alone or before or after using tamoxifen, another drug to prevent cancer recurrence. Women may use aromatase inhibitors for up to five years, even after five years of tamoxifen use, according to the recommendations.

Aromatase inhibitors and tamoxifen work differently and have different side effects. But the studies reviewed by a panel of experts who wrote the new guidelines found that aromatase inhibitors, either taken alone or combined with tamoxifen therapy, reduced the risk of cancer recurrence compared with tamoxifen alone. Use of an aromatase inhibitor reduced the risk of cancer returning the same breast, occurring in the opposite breast or spreading elsewhere in the body compared with tamoxifen alone.

The panel found no significant differences between the three brands of aromatase inhibitors on the market. Aromatase inhibitors are only effective in post-menopausal women, while tamoxifen can be used by pre- menopausal women with breast cancer. The American Society of Clinical Oncology has a patient guide on the medications at cancer.net.