Breast Cancer Gene Expression Tests
Tests 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. This is information doctors can use 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 cells 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.
It’s important to know that these tests can cost a lot and aren’t always covered by insurance.
How are the tests done?
Oncotype DX®: The Oncotype DX test is used for small hormone receptor-positive tumors (1 cm or less) that have not spread to lymph nodes, but it may be used for more advanced tumors, too. It also can be used for DCIS (ductal carcinoma in situ or stage 0 breast cancer).
This test looks at a set of 21 genes in 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 chemotherapy.
- A lower score means a low risk of recurrence. Women with low-recurrence scores would probably not benefit from chemotherapy.
- A high score means a high risk of recurrence. Women with high-recurrence scores are likely to benefit from chemotherapy to help decrease 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 are now being looked at 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.
Agendia website: Mammaprint. Accessed at www.agendia.com/healthcare-professionals/breast-cancer/mammaprint/ on September 29, 2015.
Genomic Health press release: Two Large International Studies Provide Additional Prospective Data Reinforcing the Ability of Oncotype DX® to Accurately Predict Clinical Outcomes in Early-Stage Breast Cancer Patients. September 28, 2015. Presentations at 2015 European Cancer Congress Complement Watershed ECOG-ACRIN/NCI TAILORx Breast Cancer Study Results Published Today in The New England Journal of Medicine. Accessed at http://investor.genomichealth.com/releaseDetail.cfm?releaseID=933281 on September 28, 2015.
Genomin Health, Inc. website: Oncotype DX. Accessed at www.genomichealth.com/en-US/OncotypeDX.aspx on September 29, 2015.
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.
Last Medical Review: June 1, 2016 Last Revised: August 18, 2016