• HER2-positive breast cancer is often treated with targeted therapies that can specifically find and kill cells that have the human epidermal growth factor receptor 2 protein.
• Other possible treatments for HER2-positive breast cancer include surgery, radiation, chemotherapy, and hormone therapy. Clinical trials may provide access to new therapies.
• Stick to your treatment plan as directed, for as long as directed, to get the best outcome and avoid negative effects.

Many treatments are now available that have been designed to specifically target HER2-positive breast cancer cells. These treatments have led to better outcomes for many individuals with this breast cancer subtype.

About 20 percent of people with breast cancer have HER2-positive tumors.

Read more details about the HER2 gene and breast cancer prognosis.

Stages of Breast Cancer Treatment

Breast cancer treatments are often given in stages. These stages are described using specific terms:

• First-line therapy, also called induction therapy, refers to the first set of treatments that you receive.
• Neoadjuvant therapy is a first-line therapy used to make a tumor smaller before it is surgically removed.
• Adjuvant therapy is prescribed to help keep cancer from returning once first-line treatments have gotten rid of the tumor.
• Second-line therapy refers to treatments a person may receive if the first-line treatments don’t work or cause too many side effects.

At various points during breast cancer treatment, your doctor may have you repeat HER2 testing. Results can help show whether the cancer is responding to treatment.

Read more about HER2 tests and diagnosis.

HER2-Positive Breast Cancer Treatments

If you have early-stage breast cancer (cancer that has not yet spread throughout the body), the goal of treatment will most likely be to eliminate the entire breast tumor. If your cancer is metastatic (has spread to other areas), you may also receive treatments to get rid of these metastases.

In cases of advanced breast cancer, however, the treatment goal may be different. You may undergo treatments that aim to make the tumor grow more slowly or ease your cancer symptoms.

The breast cancer treatment plan that is best for you will likely be very different from the treatment plan for someone else. Several considerations go into deciding which cancer treatment plan is a good fit for your needs, including:

• Your age
• Other health conditions you may have
• The type of breast cancer you have
• The stage and grade of your tumor
• Whether you are premenopausal (still having your period) or are postmenopausal (have gone through menopause)
• Genetic changes found in your tumor
• Your preferences regarding health care

1. Targeted Therapy

People with HER2-positive breast cancer often begin treatment by receiving targeted therapy. Medications in this category are often given as both neoadjuvant and adjuvant treatments. Targeted therapies can specifically recognize and kill HER2-positive breast cancer cells.

Monoclonal Antibodies

The immune system makes proteins called antibodies to fight harmful things like viruses and cancer. Each antibody can recognize and attach to a specific substance, such as a particular protein or cell and signal to the rest of the immune system to attack that target.

Antibodies can be manufactured in a laboratory and designed to attack targets on cancer cells. When antibodies are manufactured, they are called monoclonal antibodies. Researchers have designed several anti-HER2 monoclonal antibodies that can recognize and attack the HER2 protein.

Trastuzumab (Herceptin) was the first monoclonal antibody approved by the U.S. Food and Drug Administration (FDA) to treat HER2-positive breast cancer. In the following years, the antibody pertuzumab (Perjeta) was also approved. The more recently approved trastuzumab-dkst (Ogivri), a biosimilar of Herceptin, is also available.

These medications:

• Attach to HER2 and prevent it from sending growth signals to the cell
• Can be taken before and after surgery
• May be taken for up to a year
• May be taken alone or prescribed with chemotherapy

Trastuzumab and pertuzumab can also be taken together. This combination increases the likelihood that all traces of cancer are removed from your body. Additionally, breast cancer cells may sometimes become resistant to one monoclonal antibody, so using a combination can be helpful.

Intravenous vs. Injection

Monoclonal antibodies are often given intravenously — that is, directly into your veins. Each dose of a monoclonal antibody may take between 30 and 90 minutes. You’ll need to go to a hospital or clinic to receive an IV infusion.

More recently, scientists have developed other forms of monoclonal antibodies that can be given subcutaneously (through an injection into the fatty tissue underneath the layer of skin). This only takes a few minutes, and you may be able to have it done at your doctor’s office.

A medication that contains these forms of monoclonal antibodies is Phesgo, a formulation of trastuzumab, pertuzumab, and hyaluronidase-zzxf that was approved by the FDA in 2020. One study found that 85 percent of people preferred subcutaneous administration of Phesgo over intravenous administration of pertuzumab and trastuzumab— primarily because the injections don’t take as long.

Kinase Inhibitors

HER2 belongs to a family of proteins called kinases. Kinase inhibitors are targeted drugs that can stop kinase proteins from doing their jobs. Drugs in this category that may be used to treat HER2-positive breast cancer include neratinib (Nerlynx), tucatinib (Tukysa), and lapatinib (Tykerb).

Kinase inhibitors are most often used to treat later-stage cancer or as a second-line treatment for earlier-stage tumors. These drugs usually come in the form of a pill that you take by mouth.

Antibody-Drug Conjugates

An antibody-drug conjugate (ADC) is a combination of targeted therapy and chemotherapy. ADCs contain a monoclonal antibody that helps the drug find cells that have the HER2 protein. The chemotherapy part of the drug then kills the cancer cell. ADC medications that may be given to people with HER2-positive breast cancer include TDM-1 or ado-trastuzumab emtansine (Kadcyla) and fam-trastuzumab deruxtecan-nxki (Enhertu).

Your doctor may prescribe an ADC as a second-line treatment for early-stage breast cancer or as a therapy for metastatic breast cancer. ADCs are usually delivered intravenously.

2. Surgery

There are several types of surgery you may receive throughout breast cancer treatment. During a lumpectomy, the tumor and a small part of the surrounding breast are removed. In a mastectomy, the entire breast is removed. Either of these surgeries may later be followed by reconstructive surgery to help repair the breast.

People with breast cancer may also undergo surgery to remove the axillary lymph nodes — small structures in your armpit that help filter harmful substances. By looking more closely at the lymph nodes, your doctor can determine whether cancer cells have begun to spread beyond the breast.

Surgery aims to remove as much of the tumor as possible from the breast. However, sometimes cancer cells remain behind in the breast or other areas of the body. Adjuvant treatments may help get rid of these remaining cells.

3. Radiation

Radiation therapy uses beams of energy, such as X-rays, that can damage cancer cells. This treatment can help reduce the chance that a tumor comes back. For people with HER2-positive breast cancer, the combination of targeted therapy, surgery, and radiation often works well to remove the cancer and keep it from coming back.

4. Chemotherapy

Individuals with HER2-positive breast cancer may receive chemotherapy treatments, also referred to as chemo. Although targeted therapies are designed to recognize specific types of cancer cells, chemotherapy is a type of drug that is intended to kill any type of cancer cell.

If you have HER2-positive breast cancer, you may receive HER2 chemotherapy medication along with targeted therapy. For example, you may take the chemotherapy drug capecitabine (Xeloda) along with kinase inhibitors to treat advanced cancer or as a second-line therapy. Chemotherapy and HER2-targeted therapy drugs are sometimes given together in regimens such as:

• TCHP — Docetaxel (Taxotere), carboplatin (Paraplatin), trastuzumab, and pertuzumab
• TH — Paclitaxel (formerly sold as Taxol) and trastuzumab
• AC-TH — Doxorubicin (Adriamycin), cyclophosphamide (Cytoxan), paclitaxel, and trastuzumab — with paclitaxel and trastuzumab specifically given after the first two drugs in the regimen

5. Hormone Therapy

HER2 is just one of several genetic changes a breast cancer cell may have. Breast tumors may also contain estrogen receptor (ER) or progesterone receptor (PR) proteins. ER and PR are types of hormone receptors. Cancer cells that have either of these proteins use hormones (chemicals in the body that act as messengers) in order to grow. Hormone therapy (also known as endocrine therapy) can block these hormones, starving the cancer cells and making it difficult for them to grow.

If you have breast cancer that is both HER2-positive and hormone receptor-positive (has either ER or PR), you may receive both targeted therapies and hormone therapies. Hormone therapy medications include tamoxifen (Soltamox) and aromatase inhibitors such as anastrozole (Arimidex). Hormone therapy may be given before or after surgery, alone, or with other treatments. This type of medication may be taken for five to 10 years.

6. New Treatment for HER2-Positive Breast Cancer

New types of treatment for HER2-positive breast cancer are continuously being studied in oncology clinical trials. If you’d like to know about other treatment options, ask your oncologist about participating in a cancer research study. Clinical trials for breast cancer treatments may offer access to treatments that are not widely available. Treatment provided in clinical trials may be free or lower in cost.

Some people may worry they’ll receive a placebo (sugar pill) during a clinical trial. In clinical studies for cancer, you will at minimum receive the standard-of-care effective treatment for your cancer type. If there’s a chance you might receive a placebo, you’ll be informed.

Partnering With Your Doctor

Shared decision-making is when you and your doctor work together to decide on the best treatment plan for you. Your role in shared decision-making is to share your goals for treatment as well as your concerns and values. You can also ask questions about anything you don’t understand.

There is no single answer to “What is the best treatment for HER2-positive breast cancer?” Your doctor’s role is to consider your preferences and help you learn more about your condition and treatment options. Your doctor will answer questions and help you weigh the potential risks and benefits of each option. Together, you will decide on the best cancer treatment plan for you. When patients are involved in decisions about their care, they are usually happier with their treatment experience.

Sticking With Your Treatment Plan

After you and your doctor decide on a plan for the treatment of breast cancer, it is important to follow your doctor’s directions. Keep taking the medication exactly as directed, for as long as directed, even if you feel better. If you don’t follow your treatment plan, or if you stop taking medication too soon, you may experience some negative effects:

• The treatments may not work as well.
• You may need to go to the doctor more often.
• You may have a higher chance of needing to go to the hospital.
• You may have a worse outcome.

If it’s hard for you to stick to your treatment plan, talk to your doctor before making any changes. They may be able to help you manage side effects or overcome other problems. Also, if you read about alternative treatments for HER2-positive breast cancer, always consult your oncologist before trying anything new.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 69,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you begun treatment for your HER2-positive breast cancer? Share your experience in the comments below, or start a conversation by posting on your Activities page.