Breast Cancer Gene Expression Tests

Gene expression tests are a form of personalized medicine - a way to learn more about your cancer and tailor your treatment.

These tests are done on breast cancer cells after surgery or biopsy to look at the patterns of a number of different genes. This process is sometimes called gene expression profiling.

The patterns found can help predict if certain early stage breast cancers are likely to come back after initial treatment. Doctors can also use the information from some of these tests to know which women will most likely benefit from chemotherapy after breast surgery.

Testing options

The Oncotype DX, MammaPrint, and Prosigna are examples of tests that look at different sets of breast cancer genes. More tests are in development. The type of test that's used will depend on your situation. Keep in mind that these tests are usually used for early stage cancers, and testing isn’t needed in all cases. For example, if breast cancer is advanced, it might be clear that chemotherapy is needed, even without gene expression testing.

Oncotype DX

The Oncotype DX test is used for stage I, II or IIIa hormone receptor-positive tumors that have not spread to more than 3 lymph nodes and are HER2 negative. 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 or surgery 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 low score (0-25) means a low risk of recurrence. Most women with low-recurrence scores do not benefit from chemotherapy and have good outcomes when treated with hormone therapy.
  • A high score (26-100) means a higher risk of recurrence. Women with high-recurrence scores are more likely to benefit from the addition of chemotherapy to hormone therapy to help lower the chance of the cancer coming back.

For women age 50 or younger who have a low recurrence score of 16-25, there might be a small to moderate benefit from the addition of chemotherapy. Talk to your doctor about your options.

MammaPrint

The MammaPrint 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 for any type of invasive breast cancer that’s 5cm (about 2 inches) or smaller and has spread to no more than 3 lymph nodes. This test can be done regardless of the cancer's hormone and HER2 status.

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.” This test is also being studied as a way to determine whether certain women might benefit from chemotherapy. 

Prosigna

The Prosigna test can be used to predict the risk of recurrence in the next 10 years in women who have gone through menopause and whose invasive breast cancers are hormone receptor-positive. It can be used to test stage I or II cancers that have not spread to the lymph nodes, or stage II cancers with no more than 3 positive lymph nodes.

The test looks at 50 genes and classifies the results as low, intermediate, or high risk.  

What do the test results mean?

Some gene expression testing 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.

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

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.

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Last Medical Review: September 20, 2019 Last Revised: September 20, 2019

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