Breast Cancer Test Recommended for Extended Endocrine Therapy

Jim Kling

May 10, 2022

In an updated clinical practice guideline, the American Society of Clinical Oncology has named the Breast Cancer Index (BCI) as the only genomic test that should be used to guide extended endocrine therapy decisions for women with early-stage, hormone receptor–positive breast cancer. The update applies to women who are node negative or have one to three positive nodes treated with 5 years of endocrine therapy and no sign of recurrence.

The update was published in the Journal of Clinical Oncology. It also gives more specific details on how to apply other, previously recommended, genomic tests to guide treatment choices.

More than half of breast cancer deaths occur after 5 years of tamoxifen therapy. The National Surgical Adjuvant Breast and Bowel Project (NSABP)- B14 trial, published in 2001, showed no benefit to extending tamoxifen therapy to 10 years, but other studies have produced mixed results.

Extended endocrine therapy may reduce the risk of recurrence, but significant side effects can impact quality of life, including osteoporosis, bone fractures, and joint pain. The uncertain benefits of extended endocrine therapy, combined with its side effects and impact on quality of life, has generated interest in genomic tests to identify patients most likely to benefit.

The BCI analyzes 11 genes from the tumor and delivers two results: the likelihood of recurrence 5-10 years after diagnosis, and whether a total of 10 years of endocrine therapy are likely to provide a survival benefit.

The 21-gene prognostic and predictive assay Oncotype DX Breast Recurrence Score, the 70-gene signature test Mammaprint, the 12-gene risk score EndoPredict, levels of Ki67 expression, and immunohistochemistry are also recommended for guiding decisions on endocrine therapy. The update included additional guidance on specific situations that each can be used. However, their usefulness for predicting recurrence at 5-10 years is unproven.

"The clinical decision to either extend or end adjuvant endocrine therapy after 5 years is a challenging decision for healthcare providers and their patients," Mark Pegram, MD, said in a press release. He is chief medical consultant for breast oncology at Biotheranostics, a subsidiary of Hologic. "There is an extensive body of clinical evidence consistently proving the utility of BCI, and its addition to major oncology clinical guidelines like those from ASCO further underscores the test's potential in clinical decision-making regarding extended adjuvant endocrine therapy."

The practice update cited five previous studies showing the ability of BCI to predict benefit from extending endocrine therapy: From 5 years of tamoxifen to 5 more years of tamoxifen; from 5 years of tamoxifen to 5 years of an aromatase inhibitor, and from 5 years of an AI to another 5 years of a drug from the same class. Most of the trials included patients who were node negative or had one to three positive nodes, so there is limited evidence supporting BCI in patients with more than three positive lymph nodes. The recommendation also applies only to postmenopausal women, as the trials included fewer premenopausal and perimenopausal women.

Several of the guideline authors reported conflicts of interest with numerous sources.

This article originally appeared on, part of the Medscape Professional Network.


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