What to Expect After a HER2-Positive Metastatic Breast Cancer Diagnosis

Petra Guglielmetti
·7 min read

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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 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”.

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.

A second type of systemic therapy your oncologist may talk about—and another option that’s useful only for HER2-positive breast cancer—is tyrosine kinase inhibitors (TKIs). A tyrosine kinase is a category of protein that includes those HER2 proteins; within cells, their job is to relay messages and act as a receptor. TKIs (which have more of those fun drug names: tucatinib, neratinib, lapatinib) interfere with that messaging—so in the case of HER2-positive breast cancer, they keep HER2 proteins from telling cancer cells to grow and divide. TKIs come in the form of pills taken once or twice a day.

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“It’s not always easy, because right now, there’s no cure for metastatic breast cancer.”

A more recent breakthrough in the treatment of HER2-positive breast cancer is a category known as antibody-drug conjugates (ADCs), which are therapies that combine antibodies with a potent anti-cancer drug. Examples include trastuzumab deruxtecan, trastuzumab emtansine (also called T-DM1 or ado-trastuzumab emtansine). When these combination treatments, given by IV, enter the body, the antibodies seek out  breast cancer cells and bind to their HER2 proteins, at which point the linked anti-cancer drug can be efficiently absorbed. This targeted process allows antibody-drug conjugates to eliminate cancer cells with minimal harm to healthy cells. The first ADC was FDA-approved for the treatment of HER2-positive metastatic breast cancer in 2013, and others have since been introduced and approved for treatment of patients with metastatic disease, with more in the research pipeline today. Studies show that ADCs have contributed to a significant improvement in overall survival rates for metastatic HER2-positive breast cancer patients.

There’s one important factor that helps determine the treatment of patients with HER2-positive metastatic breast cancer: whether breast cancer cells are hormone-receptor positive—meaning certain hormones are helping the cancer to grow. About half of HER2-positive cancers have hormone receptors. If you’re HER2-positive and your cancer cells also have estrogen receptors (“ER-positive”) or progesterone receptors (“PR-positive”), your breast cancer is what’s called “double-positive.” If, more rarely, HER2-positive breast cancer cells have receptors for both estrogen and progesterone, that’s known as “triple-positive” breast cancer. The good news that comes with being hormone-receptor-positive: Your breast cancer treatment options also include endocrine therapy, drugs that prevent the body from producing the specific hormones that are helping cancer grow and spread. The five-year survival rates for people with HER2-positive metastatic breast cancer who are hormone-receptor positive are slightly higher than those who are negative.

How people feel during treatment for HER2-positive metastatic breast cancer varies. Beyond any breast cancer symptoms and side effects that may accompany radiation or chemotherapy, many of the targeted treatments used specifically to target HER2-positive breast cancer do come with some side effects of their own. It’s important to note that if there’s any chance you’re pregnant, you should avoid anti-HER2 drugs due to fetal toxicity. For that reason, it’s also important to use effective birth control while undergoing treatment for HER2-positive breast cancer. Monoclonal antibodies also have the potential to lead to heart problems, so your doctor will carefully screen you before they’re administered. When you’re being treated using these drugs, let your doctor know immediately if you develop symptoms like an elevated heart rate, swollen legs, extreme fatigue, or shortness of breath. Depending on which specific drugs you’re treated with, other side effects may include diarrhea, nausea, and liver problems. You can also ask your health care provider about palliative care, which helps manage side effects as well as any symptoms from breast cancer to minimize discomfort as you undergo treatment.

Since metastatic breast cancer can’t be eliminated, the goal of your treatments will be progression-free survival—meaning the cancer is not spreading and no new symptoms are occurring. In order to monitor your cancer, you’ll need to undergo regular blood tests and scans. Despite the rapid advances being made when it comes to the treatment of patients with HER2-positive metastatic breast cancer, which have led to an improved outlook for survival rates, patients still develop resistance to therapies over time, at which point cancer will progress. It’s important to contact your health care provider if you notice new changes in your breasts or your body, or develop any kind of new symptom, as these may be signs that your breast cancer has spread and that your treatment plan needs to be adjusted. As a later-line treatment option, people with HER2-positive breast cancer often have opportunities to participate in a clinical trial, which gives you access to promising treatments that haven’t yet been FDA-approved and also allows you to be part of the process of finding the next breakthrough when it comes to metastatic breast cancer. (Example: the successful 2020 clinical trial called Her2Climb, which demonstrated the effectiveness of treatment with a tyrosine kinase inhibitor in combination with two other therapies.) To find out more about what to expect when you have HER2-positive metastatic breast cancer, read one woman’s firsthand account of her diagnosis, as told to Glamour, and visit our metastatic breast cancer map for more personal stories and updates on efforts to find new treatments and a cure.

For more information on HER2-targeted therapies for metastatic breast cancer, visit Susan G. Komen.

Petra Guglielmetti is a health, wellness, and beauty journalist who taps into a broad network of doctors, scientists, and medical experts to write in-depth service articles for leading publications like Glamour, Health, Real Simple, and Parents.

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Originally Appeared on Glamour