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What You Need to Know About Targeted Therapy for Breast Cancer

The goal of targeted therapy for breast cancer

One type of treatment that may be used for breast cancer is called targeted therapy. It uses molecularly-targeted drugs. This means the drugs zone in on specific proteins that allow cancer cells to grow and spread.

Specific kinds of targeted drugs for breast cancer include monoclonal antibodies and tyrosine kinase inhibitors. They work by stopping or slowing the growth of some breast cancers 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.

The most common monoclonal antibody drug used to treat HER-2 breast cancer is Herceptin (trastuzumab). About 20 percent of breast cancer tumors 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. Treatment with Herceptin can stop or slow the growth of these cancer cells. Improvements in targeted therapy drugs are becoming available, such as the FDA-approved use of ado-trastuzumab emtansine. 

Perjeta (pertuzumab) is another 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.

Tykerb (lapatinib) is a tyrosine kinase inhibitor that 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 Herceptin.

Making the decision to have targeted therapy

Your doctor may suggest targeted therapy if your breast cancer is found to be HER-2 positive. Targeted therapies focus on the cancer cells and tend to have milder side effects than chemotherapy. You may take these drugs alone, but they are also given along with chemotherapy.

Targeted therapies are not without side effects and you should discuss these with your doctor. Before you take a targeted therapy, ask your doctor if you’re taking a class of chemotherapy drugs that includes Adriamycin (doxorubicin) or Ellence (epirubicin). Taking these drugs with targeted therapies for breast cancer can cause heart problems. You need to know what to watch for so you can tell your doctor about problems right away.

Many other targeted therapies are being studied for breast cancer, too, especially in the treatment of advanced breast cancers. Talk with your doctor to find out if one of these treatments is right for you.

Online Medical Reviewer: Freeborn, Donna, PhD, CNM, FNP
Online Medical Reviewer: newMentor board-certified, academically affiliated clinician
Last Review Date: 9/9/2013
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