• Targeted therapy works by targeting specific proteins unique to breast cancer cells.
• The type of targeted therapy that will work for you depends on the genetic details of your breast cancer.
• If you experience side effects while taking targeted drugs, your cancer care team can help you find ways to manage and reduce them.

Targeted drugs are relatively new treatments for breast cancer. Targeted therapy for breast cancer uses drugs directed at specific protein targets that cancer cells need to grow and live longer. Targeted drugs treat cancer by killing or slowing the growth of breast cancer cells.

Many different types of targeted therapy can be used to treat breast cancer. If you have breast cancer, targeted therapy may be included in your treatment plan at any phase of treatment, before or after surgery.

What Is Targeted Therapy?

Cancer cells have changes that make them different from the normal cells in your body. These changes are usually caused by abnormal genes that control which proteins the cell makes and how the cell functions. Cancer cells often have gene changes that allow them to grow out of control. Targeted drug therapies are directed at proteins in cancer cells to destroy them or slow their growth.

The targeted drugs are directed at proteins that are unique to cancer cells, so these drugs do not affect normal cells the same way as chemotherapy. Chemotherapy kills all fast-growing cells, regardless of whether they are normal cells or cancer cells.

When Is Targeted Therapy Used for Breast Cancer?

Targeted therapy can be used during any step of breast cancer treatment, either before or after surgery. In some cases, targeted therapies may be taken as long-term maintenance treatment to prevent relapse, sometimes for years after other breast cancer treatments are complete.

Targeted therapy is used to treat several types of breast cancer, including:

• Hormone receptor-positive breast cancer (positive for estrogen receptors or progesterone receptors — ERs or PRs)
• HER2-positive breast cancer
• Women with BRCA gene mutations
• Triple-negative breast cancer

Your doctor will make sure you are using the right targeted therapy for your type of cancer. They may test the blood or biopsy samples of your cancer to see if the specific target of the therapy is present in the cancer cell.

Targeted therapies may be used alone or in addition to other treatments, like chemotherapy or radiation therapy. In some cases, targeted therapy can work even when chemotherapy drugs don’t.

How Is Targeted Therapy Taken?

Your treatment plan will depend on the type of cancer you have. Talk to your cancer team about what to expect during your treatment.

Depending on the drug, targeted treatments may be taken as a pill, given as a shot under the skin (subcutaneously), or injected intravenously (into a vein, IV). If you receive targeted therapy by a shot or IV, you may go to a cancer treatment center to receive your dose. Or, you may be able to take a pill at home.

Depending on which targeted therapy you take, you may take it every day, once a week, once a month, or sometimes less frequently.

Doctors, pharmacists, and nurses take special precautions to protect themselves while they treat you with targeted drugs or other cancer treatments. They may wear protective clothing, gloves, goggles, or face shields.

Types of Targeted Therapy for Breast Cancer

Targeted therapy zeroes in on specific processes that are more common in cancer cells than healthy cells.

Certain targeted therapies will affect processes that keep cancer cells from growing or dividing, or cause cancer cell death. Targeted drugs can also be attached to chemotherapy drugs to bring the chemotherapy directly to where the cancer is. If your doctor recommends targeted therapy as part of your treatment plan, it’s because that target has been identified on your breast cancer cells.

Monoclonal Antibodies

Monoclonal antibodies are proteins that are made in a laboratory. These antibodies are designed to target specific proteins in cancer cells.

Some monoclonal antibodies are also considered immunotherapy when they target the immune system instead of cancer cells.

For example, for the treatment of HER2-positive breast cancer, monoclonal antibodies are designed to attach to the HER2 protein, which affects how the cell grows. When antibodies attach to HER2, it can stop cancer cells from growing.

Monoclonal antibody drugs used to treat breast cancer can be given by IV or subcutaneously and include:

• Trastuzumab (Herceptin)
• Pertuzumab (Perjeta)
• Margetuximab (Margenza)

Antibody-Drug Conjugates

When a chemotherapy drug is attached to an antibody, it is called an antibody-drug conjugate. For breast cancer treatment, antibodies made to target HER2 can be attached to chemotherapy drugs to bring the chemo drugs directly to the cancer cells.

Examples of IV antibody-drug conjugates include:

• Ado-trastuzumab emtansine (Kadcyla)
• Fam-trastuzumab deruxtecan (Enhertu)
• Sacituzumab govitecan (Trodelvy)

Kinase Inhibitors

Kinases are proteins that act as messengers in cells, delivering messages to different parts of the cell. Drugs that block kinases are called kinase inhibitors and are pills taken by mouth. Breast cancer therapy focuses on targeting kinases that are involved in cell growth. Blocking this process can slow down how fast breast cancer cells grow.

Your doctor may refer to some of these drugs by the type of kinase the drug targets. Some of the kinases that can be targeted in breast cancer include HER2, CDK4/6, mTOR, and PI3K.

Anti-HER2 kinase inhibitors include:

• Lapatinib (Tykerb)
• Neratinib (Nerlynx)
• Tucatinib (Tukysa)

CD4/6 inhibitors include:

• Palbociclib (Ibrance)
• Ribociclib (Kisqali)
• Abemaciclib (Verzenio)

Everolimus (Afinitor) is an mTOR inhibitor. Alpelisib (Piqray) is a PI3K inhibitor.

PARP Inhibitors

Poly (ADP-ribose) polymerase (PARP) is a protein found in cells that helps damaged cells to repair themselves. PARP inhibitors stop these proteins from doing their job, so cells can’t repair themselves.

People who have abnormal changes (mutations) in the BRCA genes also have trouble repairing damage to those cells. When a person with a BRCA mutation takes a PARP inhibitor, cancer cells can’t repair themselves and will die. These medications are taken by mouth and can only be taken by women with a BRCA mutation. Examples of PARP inhibitors include olaparib (Lynparza) and talazoparib (Talzenna).

Special Precautions When Taking Targeted Therapy by Mouth

Many targeted drugs are available as pills that are taken by mouth and can be taken at home. Some targeted drugs can be dangerous to others. Store your medication where others won’t come into contact with it. Make sure friends and family do not come into contact with your body fluids while you’re taking targeted drugs and for a time after you are finished.

Before starting a targeted drug therapy at home, ask your doctor or pharmacist questions about how to handle and store these drugs. Some questions include:

• Do I need to wear gloves to touch the pills?
• What precautions should I take to protect my friends and family?
• Do the pills have to stay in the bottle they came in?
• How do I dispose of the empty bottle?

Side Effects of Targeted Therapy

Like all drugs, even those you can buy over the counter, targeted drugs have side effects. Everyone is different — some people will have few or no side effects, while others may have serious problems. The side effects you experience depend on the type of treatment you are taking and the dose.

Talk to your cancer care team about the side effects specific to the targeted therapy you will be taking. Your doctor can recommend ways to prevent or manage the severity of many side effects.

Short-term side effects can start during treatment with targeted therapy and can go away over time after you finish your treatment. The amount of time it takes for side effects to improve is different for everyone.

Some of the common side effects of targeted drugs are similar to chemotherapy. They are usually short term, including:

• Skin changes
• Nausea or vomiting
• Liver problems
• Diarrhea or constipation
• Sores in your mouth
• Trouble breathing
• Fatigue
• Cough
• Headache
• Hair loss
• Increased risk of infection

Some people can have serious side effects when taking targeted drugs, including:

• High blood pressure
• Bleeding or clotting problems
• Slow wound healing
• Heart damage
• Autoimmune reactions
• Swelling

Your cancer care team will monitor you closely to check for side effects. Let your doctor know about any changes in how you feel during and after your treatment.

Long-Term Side Effects

Targeted drugs are still new, so researchers are still learning whether there may be long-term side effects. Scientists do know that some side effects of cancer treatment, like heart damage caused by chemotherapy, can last a lifetime. You may hear more about the long-term side effects of targeted therapy in the coming years after more clinical trials are completed.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 59,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you taken a targeted drug therapy for breast cancer? Share your experiences in the comments below, or start a conversation by posting on your Activities page.