You’ve been diagnosed with breast cancer. The doctor tells you you’re HER2 positive. What does that mean? And how will it direct your treatment?
Q. I’ve been diagnosed with breast cancer, and while explaining the results of my pathology report, the oncologist told me the cancer is probably "HER-2/neu positive." What does that mean, exactly?
A. All cells do three things: they grow, they rest, and they repair themselves. Genes inside the chromosomes in your cells regulate their activity, telling them when to grow, and when to stop growing and rest. If the genes malfunction, the patterns of growth/rest/repair are disrupted. "¨"¨
In HER2-neu positive (HER2+) breast cancer, there’s an excess (or overexpression) of HER2 genes in the chromosomes of some of your cells. These genes tell the cells to grow extra protein receptors on their surface. With these extra receptors, the cells keep getting signals to grow, rather than to rest or repair. They grow much faster than the cells around them; and this wild, uncontrolled growth makes them much more aggressive than "normal" cancer cells.
Twenty to 25 percent of all cases of breast cancers are HER2-positive. So, while being HER2+ isn’t the norm, you have plenty of company. And more important, it’s common enough that your oncologist will know the best way to treat it.
Q. Let me back up; the oncologist said "probably" HER2+. How come he’s not sure?
A. There are two ways to test if your cancer is HER2+. Why two? Well, it’s like wearing your seatbelt plus having an airbag in your car; if one doesn’t work, the other will.
The first, less expensive test, immunohistochemistry (IHC), determines whether or not your cancer is overexpressing the HER2 gene. If the result comes back +3, then the test is positive; your cancer is HER2+.
However, if the test comes back negative, +1, or +2, it’s deemed "questionable." In that case a second test, fluorescence in situ hybridization (FISH), is given. FISH, a more precise test, can determine for sure whether your cancer is HER2+.
So, your tumor may have been tested with just IHC initially, and it came back, say, +2. So now your oncologist will order the FISH test, to confirm that your cancer is HER2+.
Q. Assuming it is in fact HER2+, how will that change my treatment?
A. Since, as mentioned earlier, HER2+ cancers are more aggressive, strong treatment is called for. And this will almost certainly mean chemotherapy, along with surgery to remove the tumor, and possibly radiation, if there’s some underlying factor your oncologist or surgeon identifies (e.g., your tumor was very close to your chest wall).
If your cancer is hormone receptive (ER/PR+), then you’ll probably take long-term hormone therapy, as well. You may also take a drug called Herceptin for a year.
Q. Tell me more about chemo"¦
Q. And what’s Herceptin?
A. Herceptin is a targeted therapy (or immune targeted therapy) drug. Targeted therapies are manufactured antibodies that "target" specific properties of cancer cells: their production of protein, their use of enzymes, or their ability to form new blood vessels to support growth. They leave healthy cells alone, which is a plus.
How does your oncologist determine if Herceptin will help you? Herceptin is usually prescribed for women whose HER2+ cancer has spread outside the breast to the lymph nodes. If the cancer hasn’t spread, you may still be advised to take Herceptin if your cancer is estrogen/progesterone negative (ER/PR-); if the tumor is larger than 2cm, and/or it’s grade 2 or 3; or if you’re under 35 years old.
Best of luck to you - there have been a lot of advances in treatment for HER2+ breast cancer over the past 10 years, and thankfully you’ll be the beneficiary of all that research.