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When HER2 Makes Breast Cancer Grow

Mistakes or changes in the way your body's cells work are a main cause of cancer. In breast cancer, one misfiring can come from the HER2 protein.

Your cancer may have too much HER2, also called human epidermal growth factor receptor 2. This can make cancer grow and spread. The good news is that testing can find this problem. Then drugs can slow or even stop this type of breast cancer.

For advanced breast cancer, your doctor may want to repeat HER2 tests after a while to see if your cancer has changed. If so, your treatment may need to change, too.

About 1 in 5 breast cancers have too much HER2 protein.  They tend to:

  • Grow quickly, spread, and come back without treatment.
  • Respond well to drugs that target the HER2 protein.
  • Respond poorly to hormonal drugs and some types of chemotherapy.

Testing for HER2

Your doctor usually tests a portion of breast cancer tissue that was removed during a biopsy or surgery. Some tests can look for HER2 genes inside a cancer cell. Other tests measure the proteins that these genes make.

You don't inherit these genes from your parents. They're a change (called a mutation) that can happen as you get older.

Your doctor may order one test first. Then, if those results are not clear, he may tell the lab to try another kind of test.

What HER2 Test Results Mean

Your cancer may be:

  • HER2-positive -- often written HER2+  
  • HER2-negative  -- often written HER2-  

What's Next?

Is your breast cancer HER2-positive? Your doctor may suggest a drug that targets the HER2 protein.

If you have been taking a drug for HER2-positive cancer, but it is no longer working, your doctor may switch you to another one. Or you may take a combination of drugs.

If your results are borderline or negative, ask your doctor whether or not it makes sense to retest. Another option to discuss is whether you can try treatment for the HER2 protein.

Your doctor may also try chemotherapy, radiation therapy, or other new types of treatment.

WebMD Medical Reference

Reviewed by Arefa Cassoobhoy, MD, MPH on January 15, 2014

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