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Breast Cancer: Targeted Therapy 

What is targeted therapy? 

Targeted therapy is the use of medicines that target parts of cancer cells that make them unlike normal cells. They do this without affecting most normal, healthy cells. The medicines are different from standard chemotherapy medicines. They may work when chemotherapy medicines don’t. And they often have less severe side effects.

How targeted therapy works 

Targeted medicines for breast cancer include monoclonal antibodies and tyrosine kinase inhibitors. They work by stopping or slowing the growth of some breast cancers. They do this by blocking certain proteins in or on the cancer cells. For breast cancer, the protein is primarily a growth factor protein called HER-2. Breast cancers that have a lot of the HER-2 protein are called HER-2 positive. About 20% of women with breast cancer have tumors that make too much of the HER-2 protein. This is called overexpression. These tumors tend to grow and spread faster than tumors that don’t make too much HER-2 protein. These tumors are also more likely to come back after treatment.

When might targeted therapy be used for breast cancer? 

Breast cancer cells are tested for HER-2 in the lab. Your doctor may advise targeted therapy if your breast cancer is found to be HER-2 positive. 

Types of targeted thera py medicines for breast cancer 

The medicines include: 

  • Trastuzumab. This monoclonal antibody medicine is the most common targeted therapy used to treat HER-2 positive breast cancer. Treatment with trastuzumab can stop or slow the growth of these cancer cells. In some cases, it can help shrink tumors.

  • Ado-trastuzumab emtansine. In this medicine, the monoclonal antibody is attached to a chemotherapy medicine. It may be used in women with advanced breast cancer who have already used trastuzumab.

  • Pertuzumab. This is a monoclonal antibody that attaches to the HER2 protein. It seems to target a different part of the protein than trastuzumab. It's given along with trastuzumab and chemotherapy to treat advanced breast cancer. This combination of medicines may also be used to treat early breast cancer before surgery is done.

  • Lapatinib. This is a tyrosine kinase inhibitor. It blocks the effects of the HER-2 protein and other proteins inside tumor cells. It may be used to treat patients with HER-2 positive breast cancer that is not responding to treatment with chemotherapy and trastuzumab.  

How is targeted therapy given for breast cancer?

These medicines may be given alone. Or they may be given along with chemotherapy. Trastuzumab, ado-trastuzumab emtansine, and pertuzumab are given as an injection into a vein. This is usually done as an outpatient procedure. This means you don’t need to stay overnight in the hospital. Lapatinib is given as a pill that you take at home in 2- or 3-week cycles. 

What are common side effects of targeted therapy?

Targeted therapy medicines work differently from standard chemotherapy. They only target certain cells, so they tend to cause less harm to healthy cells. They also often have less severe side effects. Possible side effects include:                                                                                                                                                                      

  • Chills

  • Diarrhea

  • Fever

  • Headaches

  • Nausea

  • Rashes

  • Trouble breathing

  • Vomiting

  • Weakness

You may find that some side effects only occur during the actual treatment. They may become less severe after your first treatment. Most side effects go away or get better within a few weeks after your treatment ends. If you're having trouble with side effects, tell your doctor or nurse so that he or she can help you manage them. 

When to call your healthcare provider

Call your doctor right away if you have: 

  • Trouble breathing

  • Leg swelling

  • Extreme tiredness

A possible serious side effect of these medicines is heart damage. This may lead to heart failure (HF). For many women, this is a short-term problem that gets better when the medicine is stopped.

The risks for heart problems are higher when certain chemotherapy medicines are given with targeted therapy. Ask your doctor if you’re taking doxorubicin or epirubicin. Taking these medicines with targeted therapy can cause heart problems. You need to know what to watch for so you can tell your doctor about problems right away.

Working with your healthcare provider

It's important to know which medicines you're taking. Write your medicines down, ask your healthcare team how they work, and what side effects they might have.

Talk with your healthcare providers about what side effects to watch out for, and when to call them. Make sure you know what number to call with questions, even on evenings and weekends.

It may be helpful to keep a diary of your side effects. Write down physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your medical team to make a plan to manage your side effects.

Online Medical Reviewer: Cunningham, Louise, RN
Online Medical Reviewer: Stump-Sutliff, Kim, RN, MSN, AOCNS
Last Review Date: 9/24/2015
© 2013 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.