Metastatic HER2-Positive Breast Cancer

Medically Reviewed by Jennifer Robinson, MD on March 17, 2023
Written by Mary Jo DiLonardo
4 min read

HER2-positive breast cancer happens when the cancer cells have higher than normal level of a protein called human epidermal growth factor receptor 2 (HER2). This protein is also in breast tissue of people who don’t have breast cancer. HER2 helps breast cells grow and multiply. It also helps them repair damage.

But sometimes mistakes in a cell’s gene cause the body to make too much HER2. This can cause breast cells to grow faster than normal. That can lead to cancer.

About 20% of breast cancers are HER2-positive. They usually grow quicker than other types of cancer.

Metastatic HER2-positive breast cancer has spread beyond the breast to other parts of the body.

Doctors don’t know exactly what causes HER2-positive breast cancer. They’re not sure why the cells grow faster in some people and not in others. They think that your environment, lifestyle, and genes can all play a part.

They do know that you can’t get a copy of the HER2 gene from your parents and you can’t pass it on to your children.

Like most breast cancers, the most common symptom of HER2-positive breast cancer is a small, hard lump in your breast.

Other signs of the condition include:

  • Breast swelling or tenderness
  • Pain in your breast or nipple
  • Redness or a thickening in your breast or nipple
  • Unusual nipple discharge
  • Irritated or dimpled breast skin

When you first find out you have breast cancer, your doctor will do several tests to learn more about it. At least one of those tests will check to see if your cancer is HER2-positive.

Those tests might include:

Immunohistochemistry (IHC) test. This measures how many HER2 proteins are on breast cancer cells.

Fluorescent in situ hybridization (FISH) test. It looks for extra copies of the HER2 gene, which make the HER2 protein.

Both of these tests usually happen on tissue taken during a biopsy.

  • How do you know I have metastasized HER2-positive breast cancer?
  • Are you sure that it has spread?
  • Where has it spread?
  • What tests should I have?
  • What are my treatment options?
  • Which treatment do you think is best for me?
  • What side effects can I expect?
  • What is my outlook?
  • Is there a clinical trial that I can be a part of?

Doctors treat metastasized HER2-positive breast cancer with several different therapies. Which treatment you'll get depends on:

  • Where it has spread in the body
  • The specific symptoms you have
  • Your overall health

Treatments can include:

Surgery. This can be one of the first steps when your doctor finds cancer. They may perform a procedure called a lumpectomy to get rid of:

  • The tumor
  • Some surrounding tissue
  • Lymph nodes

In some cases, your doctor might remove the entire breast. This is called a mastectomy.

Targeted therapy. This uses a group of drugs made specifically for HER2-positive breast cancer. They target specific tissue types, genes, or proteins that play a part in cancer growth. There are different types of these drugs that work in different ways. Which ones your doctor will give you depend on which treatments you've already tried.

For example, tucatinib (Tukysa) is for people with advanced HER2-positive breast cancer. It's often taken with trastuzumab (Herceptin) and capecitabine (Xeloda) when the cancer has spread to other parts of the body.

Trastuzumab often goes along with chemotherapy or hormonal therapy.

Chemotherapy. Given by IV or pill, chemotherapy kills cancer cells throughout the body. It’s a common treatment for HER-2 positive breast cancer. Often, doctors give it before surgery, after surgery, or both. People with advanced cancer often take it for 4 to 6 months.

Radiation. You would usually get this after surgery to get rid of any leftover cancer cells. It’s usually in the form of high-energy X-rays. Radiation is also a popular choice when cancer has spread to the brain.

Hormone therapy. Sometimes cancer can be "hormone receptor positive," which means it needs estrogen to grow. If that’s the case with your cancer, you can take drugs to lower your levels or block how estrogen works in your body.

Clinical trials. These are studies that test new ways to treat HER2-positive breast cancer. They look at the safety of proposed treatments and whether they work. Often, you'll get these treatments free of charge. Ask your doctor if you might be a good fit for a clinical trial.

It can be very stressful to have cancer. It can be easier to handle when you take care of your body and mind.

There are different things that can help.

Eat healthy and exercise. Make sure fruits and vegetables have a big role in your menu. Also:

  • Get plenty of exercise.
  • Cut back on alcohol.
  • Kick the habit if you smoke.

Keep up with your doctor visits. Don’t miss any appointments, and reach out to your doctor whenever you have questions.

There's no cure for metastatic cancer. Your cancer may stop responding to a specific treatment, so it’s not unusual for you to have to switch and try a different one.

How well treatments work depends on how much the cancer has spread and which other therapies you've tried. The right treatment can help give you a good quality of life for many months or years.

If you feel overwhelmed by your diagnosis or treatment, don’t be shy about reaching out for help. Ask your doctor any questions you might have. Your medical team can help learn more about your cancer.

Talk to family and friends and let them know how you are feeling. Ask for help when you need it or tell them when you just want to talk.

If you’d rather talk to people who are going through the same things you are, find a cancer support group. The American Cancer Society can help you.