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Oncotype DX Test for Breast Cancer

The Oncotype DX test can help predict whether your breast cancer will return so that you and your doctor can choose the best treatment right from the start. It's often used to help decide who needs chemotherapy after surgery and who can safely avoid chemo.

This lab test is usually done when you are first diagnosed, using the tissue sample taken during a biopsy or surgery. You may hear it called a 21-gene signature. The test is most helpful for women with an early-stage cancer that fits this description:

  • Stage I or II invasive breast cancer
  • Estrogen-receptor positive (called ER+), meaning the cancer cells grow in response to the hormone estrogen
  • No cancer in the lymph nodes

Oncotype DX may also help guide your treatment choices when cancer has spread to the lymph nodes.

The test does not need to be ordered if:

  • Your cancer has high amounts of the protein HER-2, which helps cancer cells grow.
  • You have a hormone receptor negative (ER-) tumor, meaning an anti-estrogen treatment is unlikely to work (and in that case you and your doctor will choose a different treatment).

Higher Score Means a Higher Risk

The test looks at 21 different genes within the cells of a tumor sample. Certain patterns suggest a more aggressive cancer that is more likely to come back after treatment. The test results show a score between 0 and 100.

  • Women with a score of 17 or smaller. You have a low risk of having cancer return, if you get a hormone treatment like tamoxifen or an aromatase inhibitor drug. With this score, chemotherapy probably won't do much to prevent a recurrence.
  • Women with a score of 18 to 30. You have a medium risk for a recurrence. Chemotherapy may help some women in this range.
  • Women with a score of 31 or more. You have a higher risk that cancer may come back. Both chemotherapy and hormone therapy (and radiation therapy for ductal cancer in situ) are likely to help women in this group.

One Factor in Many

Oncotype DX test results are not enough on their own to guide treatment. Your doctor will consider your test score along with other aspects of your cancer to decide on the best treatment. These factors can include the tumor size and grade, the number of hormone receptors in your cancer (many or just a few), and your age.

A large study called the TAILORx trial is under way with women who have a mid-range score. Researchers want more precise information on which types of breast cancer need chemo to stop them from coming back, and which cancers don't.

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