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How long to take aromatase inhibitors?

Page last modified on: November 20, 2008

Question from Wizzy: Any research results on how long to take aromatase inhibitors?: Answers —Hope Rugo, M.D.: The standard length of treatment with hormone therapy (tamoxifen in the past) was five years. The aromatase inhibitor trials in the adjuvant setting have looked at 5 years of hormone therapy. This is a total of five years whether patients start with an aromatase inhibitor or whether they switch after two or three years of tamoxifen.

There is one study that looked at continuing hormone therapy with an aromatase inhibitor after 5 years of tamoxifen and showed very striking results in reducing recurrence. However, we don't have data on women who took five years of aromatase inhibitor after diagnosis.

Until we have better information on length of therapy, aromatase inhibitors should be stopped after five years, as we don't have evidence on possible risks or benefits to their cancer after this length of time. The story is different if you start with tamoxifen. A women who has taken five years of tamoxifen who is going to Letrozole (Femara) as extended therapy could continue this therapy anywhere from three to five years. But only about 1,200 women made it to four years before the study closed.; Jennifer Armstrong, M.D.: So if a woman starts with tamoxifen for two years, you would discontinue the aromatase inhibitor after five years?; Hope Rugo, M.D.: Yes, this is different than a woman who received tamoxifen for five years and then is switched to an aromatase inhibitor. In this latter situation, an aromatase inhibitor may be considered for anywhere from two to five years.

On Wednesday, June 15, 2005 our Ask-the-Expert Online Conference was called Updates from the 2005 ASCO Annual Meeting. Hope Rugo, M.D. and moderator Jennifer Armstrong, M.D. answered your questions on the latest research advances presented at the 2005 American Society of Clinical Oncology meeting in Orlando, FL.

The materials presented in these conferences do not necessarily reflect the views of breastcancer.org. A qualified healthcare professional should be consulted before using any therapeutic product or regimen discussed. All readers should verify all information and data before employing any therapies described here.

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Meet the Experts

Hope S. Rugo, M.D. is a clinical professor of medicine in the division of hematology and oncology at the University of California San Francisco (UCSF) Helen Diller Family Comprehensive Cancer Center, where she directs the Breast Oncology Clinical Trials Program.

Jennifer Armstrong, M.D. is a breast cancer oncologist at Paoli Hematology-Oncology Associates in Paoli, Pa., with a special interest in physicians' communication skills.