Will Herceptin Work for You?

If you are one of the 25% of women with metastatic breast cancer with tumors that have too many copies of the HER2 gene or too many HER2 receptors, Herceptin may work to slow down or stop the growth of the cancer. Read an article about Herceptin after chemotherapy.

Two tests are used to figure out if the cancer is likely to respond to Herceptin. One test measures HER2 receptor protein (IHC), and the other test counts copies of the HER2 gene (FISH):

1. IHC (ImmunoHistoChemistry)

   IHC is the most commonly used test to see if a tumor has too much of the HER2 receptor protein on the surface of the cancer cells.

   The IHC test gives a score of 0 to 3+ that indicates the amount of HER2 receptor protein in tumors. If the tumor scores 0 to 1+, it's called "HER2 negative." If it scores 2+ or 3+, it's called "HER2 positive."

   Women with IHC positive scores tend to respond favorably to Herceptin. The drug is not considered effective for tumors with IHC scores of 0 or 1+.

   It's important to remember that results on the IHC test may vary from lab to lab, and that some labs are more proficient at HER2 testing than others. Discuss with your doctor whether you might want to get a FISH test, especially if you have a 1+ or 2+ result from IHC. That way you can get another measure of whether the tumor might respond well to Herceptin.

   The IHC test results are most reliable for fresh or frozen tissue samples. IHC tends to be an unreliable way to test tissue that's preserved in wax or other chemicals. FISH testing is the preferred way to assess preserved tissue samples.

2. FISH (Fluorescence In Situ Hybridization)

   The FISH test looks for the HER2 gene abnormality. This test is the most accurate, but less available, way to find out if a breast tumor is likely to respond to Herceptin. The FISH test shows how many copies of the HER2 gene are in tumor cells. This gene directs cells to make the HER2 protein. The more copies of the gene, the more HER2 receptors the cells have.

   With the FISH test, you get a score of either "positive" or "negative" (some hospitals call a negative test "zero"). If the tumor is "FISH positive," it will probably respond well to Herceptin.

You can find out more about these tests, and how the results are reported in your pathology report, in our section on Your Pathology Report.

Herceptin is currently approved by the U.S. Food and Drug Administration for:

• women with metastatic HER2-positive disease
• women with earlier stages of HER2-positive disease as adjuvant treatment (treatment after initial treatment, such as surgery) as part of a regimen containing Adriamycin (chemical name: doxorubicin), Cytoxan (chemical name: cyclophosphamide), and Taxol (chemical name: paclitaxel)