Breast Cancer Gene Expression Tests

Tests done after surgery or biopsy that look at the patterns of certain genes (sometimes called gene expression profiling) can help predict if some early-stage (stage 1 or 2) breast cancers are likely to come back after initial treatment. Doctors can use this information to know which women will most likely benefit from chemotherapy after breast surgery.

What are gene expression tests?

Looking at the patterns of a number of different genes at the same time can help predict if certain stage 1 or 2 breast cancers are likely to come back after initial treatment. Tests like these are part of what’s being called “personalized medicine” – learning more about your cancer to specially tailor your treatment.

The Oncotype DX® and the MammaPrint® are examples of tests that look at different sets of breast cancer genes. And there are more tests in development.

How are the tests done?

Oncotype DX®: The Oncotype DX test is used for small hormone receptor-positive tumors that have not spread to more than 3 lymph nodes, but it may be used for more advanced tumors, too. It can also be used for DCIS (ductal carcinoma in situ or stage 0 breast cancer).

This test looks at a set of 21 genes in cancer cells from tumor biopsy samples to get a “recurrence score,” which is a number between 0 and 100. The score reflects the risk of the breast cancer coming back (recurring) in the next 10 years and how likely you will benefit from getting chemo after surgery.

  • A lower score (usually 0-10) means a low risk of recurrence. Most women with low-recurrence scores probably do not benefit from chemotherapy.
  • An intermediate score (usually 11-25) means an intermediate risk of recurrence. Most women with intermediate-recurrence scores probably will not benefit from chemo, although women younger than 50 with a higher intermediate score (16-25) might. Women in this group should discuss the possible risks and benefits of chemo with their doctor.
  • A high score (usually 26-100) means a higher risk of recurrence. Women with high-recurrence scores are more likely to benefit from chemo to help lower the chance of the cancer coming back.

MammaPrint®: This test can be used to help determine how likely breast cancers are to recur in a distant part of the body after treatment. It can be used in any type of breast cancer that’s small (stage 1 or 2) and has spread to no more than 3 lymph nodes. Hormone and HER2 status are assessed as part of this test.

The test looks at 70 different genes to determine if the cancer is at low risk or high risk of coming back (recurring) in the next 10 years. The test results come back as either “low risk” or “high risk.”

What do the test results mean?

Gene expression testing (gene profiling) can help predict which women will most likely benefit from chemotherapy after breast surgery. (This is called adjuvant chemotherapy.) Hormone therapy is a standard treatment for hormone receptor-positive breast cancers, but it’s not always clear when to use chemotherapy. These tests can help guide that decision.

Still, these tests cannot tell any one woman for certain if her cancer will come back with or without chemotherapy. Many doctors use these tests (along with other information) to help make decisions about offering chemotherapy. Keep in mind that these tests aren’t needed in all cases. For instance, if you have a fast-growing or a stage 4 breast cancer, you don’t need these tests because you should get chemotherapy as part of standard treatment.

These tests continue to be studied in large clinical trials to better understand how and when to best use them. In the meantime, women might want to ask their doctors if these tests might be useful for them. 

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

National Comprehensive Cancer Network (NCCN). Practice Guidelines in Oncology: Breast Cancer. Version 2.2017. Accessed at on August 18, 2017.

Agendia website: Mammaprint. Accessed at on August 22, 2017.

Genomic Health, Inc. website: Oncotype DX. Accessed at on August 22, 2017.

Paik, S. Development and Clinical Utility of a 21-Gene Recurrence Score Prognostic Assay in Patients with Early Breast Cancer Treated with Tamoxifen. The Oncologist. 2007;12(6): 631-635.

Sparano JA, Gray RJ, Makower KI, Pritchard KS, Albain DF, Hayes CE, et al. Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer [published online ahead of print June 3 2018]. NEJM. 2018; doi: 10.1056/NRJMoa1804710.

Last Medical Review: September 25, 2017 Last Revised: January 25, 2019

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