Do All Breast Cancer Patients Need 10 Years of Anti-Estrogen Therapy?

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Whether you have just recently been diagnosed with breast cancer, or are currently undergoing treatment, it’s important to be well informed about your diagnosis and the road ahead. If your doctor has told you that you are a candidate for anti-estrogen therapy, you may be wondering how long you will need to take this therapy.

Women who undergo anti-estrogen therapy typically receive this treatment for a minimum of five years. However, recent research has shown that some women may benefit from extended anti-estrogen therapy for a total of 10 years.

Who Is a Candidate for Anti-Estrogen Therapy?

Women who are diagnosed with hormone receptor positive breast cancer are recommended for anti-estrogen hormone therapy treatment. Hormone receptor positive breast cancers grow more rapidly in the presence of estrogen because they contain hormone receptors that respond to this hormone.

Anti-estrogen medications, such as tamoxifen and aromatase inhibitors, are the most common forms of treatment for hormone receptor positive breast cancer. These therapies help prevent the risk of recurrence by either limiting the amount of estrogen available to bind to receptors that encourage tumor growth or reducing the amount of estrogen in the body.

Who Benefits From 10 Years of Anti-Estrogen Therapy?

New research shows that some women may benefit from extending anti-estrogen therapy for an additional five years after completing an initial five-year treatment period. However, the biology of each woman’s tumor is different, and therefore not everyone benefits from extended treatment.  In fact, only about 3-5 out of 100 patients benefit from extended anti-estrogen therapy.1-5  It is therefore important to weigh the risk vs. benefit of continuing anti-estrogen therapy for more than 5 years to determine the best treatment option for you.

Learning More About Your Personal Risk of Recurrence

If you are an ER+, early-stage breast cancer patient, a tool called the Breast Cancer Index test may help you and your doctor by providing your personal risk of a metastatic  recurrence after year 5 and likelihood of benefit from extended (5 more years) anti-estrogen therapy. This test analyzes cells from the original tumor biopsy to study the expression of specific genes in the tumor.

Your doctor will receive a result with two important pieces of information. One piece will provide a number that indicates your specific risk of late cancer recurrence, the risk of cancer coming back after 5 years. The second piece is an assessment of the likelihood that an additional five years of anti-estrogen therapy will help lower your risk of recurrence.  No other test provides this piece of information. The results of the test are unique to your tumor and, when assessed with all your clinical information, provide valuable information that allows you and your doctor to make important decisions about your treatment plan.

Talk to Your Doctor About Your Diagnosis

Not all breast cancer patients benefit from 10 years of anti-estrogen therapy. Talk to your doctor about your specific diagnosis and to learn if you may benefit from additional anti-estrogen therapy.


1. Goss PE, et al. J Natl Cancer Inst . 2005;97:1262-1271. 2. Davies C, et a l .L ancet . 2013;381:805-816. 3. Gray RG, et al. J Clin Oncol . 2013;31(suppl):abstract 5. 4. Goss P et al. New Engl J Med 2016 DOI: 10.1056/

NEJMoa1604700 5. Mamounas EP et al. NSABP B-42. S1-05. SABCS 2016 Dec 7, 2016


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