HER2-positive breast cancers have too many copies of the HER2/neu gene. HER2-positive breast cancers make too much of the HER2 protein, which receives signals telling the breast cancer to grow. About 1 out of every 4 breast cancers is HER2-positive.
HER2-positive breast cancers tend to be more aggressive than HER2-negative breast cancers. Herceptin (chemical name: traztuzumab) and Tykerb (chemical name: lapatinib) are targeted therapy medicines used to treat HER2-positive breast cancers. Figuring out the HER2 status of a breast cancer is an important first step in deciding if these targeted therapies may be a good treatment option.
A study evaluated the results from a number of earlier studies. The researchers found that HER2 testing as well as the way the test results were recorded in medical and insurance records were inconsistent and generally inadequate.
In many cases:
- HER2 testing wasn't done at all; in one study only half of the women diagnosed with metastatic breast cancer had HER2 testing to guide treatment decisions.
- HER2 testing was done but the results weren't recorded in a woman's medical or insurance records.
- Women were treated with Herceptin without having HER2 testing or were treated based on test results that were either negative or inconclusive.
In one earlier study, most women (90%) had only an IHC (immunohistochemistry) HER2 test performed, which is the less reliable type of HER2 test. The results weren't confirmed by the more reliable FISH (fluorescence in situ hybridization) test. When IHC test results are considered "borderline," experts recommend that a FISH test be done to determine HER2 status.
If you've been diagnosed with breast cancer, the information in your pathology report -- including HER2 status -- gives your doctor important details about the "personality" of the cancer. Knowing all the details about the cancer is essential to develop a treatment plan that makes the most sense for your specific situation.
Take the time to talk to your doctor about ALL of the information in your pathology report. Ask your doctor about any missing or incomplete information and any assumptions that are being made that could influence treatment decisions. Make sure HER2 testing was done and ask which type of test was performed. Many labs perform the IHC test as the standard test. A reading of 0 or 1+ is considered negative. A 3+ reading is considered positive. If your IHC result is 2+ (which is considered borderline), ask about having a FISH test done to more conclusively determine the cancer's HER2 status.
The Breastcancer.org Your Diagnosis pages offer more information about the information that should be in your report, as well as more about HER2 status and testing.