Back January 19, 2017

Knowledge is Power: Three Important Things to Know about Recent Clinical Trials on Extended Aromatase Inhibitor Therapy

Last month at the San Antonio Breast Cancer Symposium (SABCS) the results of three extended anti-estrogen therapy trials were presented that could have a big impact on the standard of care for ER+ breast cancer patients and survivors.

You may have heard buzz about the trial results, and what they mean for the ER+ breast cancer community. The NSABP B-42, DATA and IDEAL trials assessed extended anti-estrogen therapy with aromatase inhibitors (AI) among postmenopausal women. Here are three things you should know.

1. The decision to extend aromatase inhibitor therapy must be individualized. While the three trials did not meet their primary goal of demonstrating a significant benefit in the entire study cohort, results from two of the studies (B-42 and DATA) were generally consistent with previous extended anti-estrogen therapy trials showing that extended anti-estrogen therapy reduced the proportion of ER+ breast cancer patients that had a recurrence by about 3-4 out of 100 women. In the B-42 trial there was a statistically significant benefit in terms of prevention of metastatic (distant) recurrences (3.9% with letrozole compared to 5.8% with placebo).

Typically, survival rates for many cancers have been measured with a five-year benchmark. In light of the data, extended anti-estrogen therapy may not be recommended for everyone. Instead, these trial data illustrate the need for individualized treatment plans, and the need to identify the women who are likely to benefit from extended treatment.

A number of variables need to be considered when determining the best course of therapy, and whether to extend beyond five years or end at year five. According to Dr. Eleftherios Mamounas, MD, MPH, Medical Director of the Comprehensive Breast Program at UF Health Cancer Center at Orlando Health and principal investigator of the B-42 trial, “Findings suggest that careful assessment of potential risks and benefits is required before recommending extended letrozole therapy to patients with early-stage breast cancer.” Questions to consider when deciding whether to continue therapy include:

  • What is your risk of recurrence after year 5?
  • What are the significant side effects and comorbidities associated with treatment?
  • What is your age?
  • How did you tolerate treatment with anaromatase inhibitor for the first five years
  • What is your bone mineral density?
  • Are you likely to benefit from continuing therapy?
  • “All of these factors figure into the potential decision of [whether to extend] therapy beyond five years or stop at five years.”12

2. Genomic testing can help you determine an appropriate course of treatment with your doctor. Physicians utilize gene expression profiling tests to help predict whether or not early-stage breast cancer is likely to come back after initial treatment, and if particular therapies are likely to be beneficial in the treatment of an individual patient. Mamounas discussed how these tests may help with treatment decisions explaining, “Genomic classifiers that predict risk of late recurrence and/or benefit from extended endocrine therapy may help further individualize the recommendation for extended aromatase inhibitor therapy”.2During a post-plenary session following the B-42, DATA and IDEAL trials presented at SABCS, Dr. Michael Gnant of the Medical University of Vienna commented on the Breast Cancer IndexSM (BCI)* as the only available test with predictive data that determines the likelihood of a patient to benefit from extended anti-estrogen therapy. Breast Cancer Index is a non-invasive test that helps physicians and patients determine whether to extend anti-estrogen therapy beyond five years by assessing both the risk of breast cancer recurrence and the likelihood of benefit from anti-estrogen therapy.

3. Having an open dialogue with your doctor is critical. It is important to work closely with your doctor to learn everything you can about your risk of breast cancer returning and all of your available treatment options. Together, you can make an informed decision to manage your diagnosis based on your medical history, the biology of your original tumor, and other individual risk factors.

What are your thoughts on the data presented at SABCS, and how can ER+ breast cancer survivors be wiser about their treatment options? Share with us on social media with the hashtag #BeWisER.

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*Breast Cancer Index Intended Use and Limitations

The Breast Cancer Index (BCI) Risk of Recurrence & Extended Endocrine Benefit Test is intended for use in patients diagnosed with estrogen receptor-positive (ER+), lymph node-negative (LN-) or lymph node positive (LN+; with 1-3 positive nodes) early-stage, invasive breast cancer, who are distant recurrence-free. BCI provides: 1) a quantitative assessment of the likelihood of both late (post-5 years) and overall (0-10 year) distant recurrence following an initial 5 years of endocrine therapy (LN- patients) or 5 years of endocrine therapy plus adjuvant chemotherapy (LN+ patients), and 2) prediction of likelihood of benefit from extended (>5 year) endocrine therapy. BCI results are adjunctive to the ordering physician’s workup; treatment decisions require correlation with all other clinical findings. This test was developed and its performance characteristics determined by Biotheranostics, Inc. lt has not been cleared or approved by the U.S. Food and Drug Administration. This test is used for clinical purposes. lt should not be regarded as investigational or for research. How this information is used to guide patient care is the responsibility of the physician. Biotheranostics is certified under the Clinical Laboratory lmprovement Amendments of 1988 to perform high complexity clinical laboratory testing.


  1. Mamounas EP, et al. NSABP B-42. S1-05. SABCS 2016 Dec 7, 2016.
  2. Sanft T, Hatzis C, Puztai. A multi-institutional, prospective study of incorporating the genomic platform Breast Cancer Index as a tool for decision-making regarding extension of adjuvant endocrine therapy. P2-09-15. SABCS 2016. Dec 8, 2016.