Understanding what it means to be diagnosed with HER2-positive metastatic breast cancer (sometimes called “HER2+ MBC” or “HER2+ breast cancer”) can feel like riding a roller coaster. Amid the initial shock and fear that accompanies any cancer diagnosis, there’s another low that comes when your oncologist tells you that this specific type of breast cancer tends to be aggressive and spread quickly. The reason lies in the “HER2-positive” part of its name: That term indicates that your breast cells have an excess of proteins called HER2 (short for “human epidermal growth factor receptor 2”), which are in charge of cell growth and division—and, of course, cells growing and diving too quickly is what leads to tumors.
That said, the real stomach-dropping, devastating moment is being told that your HER2-positive breast cancer is metastatic, also known as MBC, stage IV, or advanced breast cancer. This means the disease has already spread significantly—beyond the breast to other parts of the body, such as your bones, brain, or other organs. Unlike early-stage cancer, metastatic breast cancer can’t be cured—regardless of HER2 status (whether you’re HER2 positive or HER2 negative). However, there are many breast cancer treatments that may be able to pause or significantly slow your disease progression while allowing you to maintain a high quality of life.
That’s where the news of a HER2-positive diagnosis takes an unexpectedly optimistic turn: Treatment options are more plentiful for breast cancer patients designated as HER2-positive. In fact, among all the types of breast cancer, HER2-positive breast cancer has one of the longest lists of effective treatment options. The reason goes back to the involvement of those HER2 proteins. You’ll be able to take advantage of highly targeted breast cancer treatments that work by specifically interfering with these cell-growth proteins, thus slowing the spread of cancer cells, without much harm to healthy cells or the lifestyle-altering side effects that other systemic treatments like chemotherapy are known for. Your oncologist may refer to these targeted treatments as “anti-HER2 therapies” or “HER2-targeted agents”. As you might guess, they’re not an option for people whose breast cancer is HER2-negative.
There are a few different types of HER2-targeted agents. One main category of HER2 therapies is monoclonal antibodies (which come with unpronounceable names like pertuzumab, trastuzumab, and margetuximab). These are administered in a healthcare setting via IV infusions or injections. Monoclonal antibodies have proven to be a highly effective tool in curing early breast cancer that’s HER2-positive, but they’re also used when managing metastatic disease over the longer term. The standard of care for treatment of patients with HER2-positive metastatic breast cancer is usually to administer monoclonal antibodies in combination with chemotherapy (commonly used drugs include capecitabine, or a category called taxanes, which includes drugs like docetaxel) and/or surgery as a first-line treatment. Depending on your response rate, your doctor will then adjust your combination of therapies as time goes on.