Breast Cancer Overview

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Treating Breast Cancer TOPICS

Targeted therapy for breast cancer

As we have learned more about the gene changes that cause cancer, researchers have been able develop newer drugs that are aimed right at these changes. These targeted drugs do not work the same as standard chemo drugs. They often have different and less severe side effects.

If you’d like more information on a drug used in your treatment or a specific drug mentioned in this section, see our Guide to Cancer Drugs, or call us with the names of the medicines you’re taking.

Drugs that target HER2

About 1 out of 5 breast cancers have too much of HER2/neu, a protein. HER2/neu is found in small amounts on the surface of normal breast cells and in large amounts on some breast cancer cells. Breast cancers that have too much of this protein are called HER2/neu-positive (or just HER2-positive). The protein makes them grow and spread faster. Certain drugs target this protein, stopping it from causing breast cancer cell growth. These drugs are:

Trastuzumab and pertuzumab are monoclonal antibodies — man-made versions of a very specific immune system protein. They are given into a vein (IV).

Ado-trastuzumab emtansine is a monoclonal antibody attached to a chemotherapy drug. It is also given IV.

Lapatinib is a targeted drug that is not an antibody. It is given as a pill.

When are these drugs used

Trastuzumab can be used to treat both early- and late-stage breast cancer. When used to treat early breast cancer, this drug is usually given for a year. For advanced breast cancer, treatment doesn’t stop after a year and can last a long time.

Pertuzumab can be given with trastuzumab and chemotherapy to treat advanced breast cancer. This combination is also used to treat early breast cancer before surgery.

Ado-trastuzumab emtansine is used to treat advanced breast cancer in women who have already been treated with trastuzumab.

Lapatinib is used to treat advanced breast cancer. It is most often used if the doctor thinks that trastuzumab is no longer working.

Side effects

The side effects of these drugs are often mild. Talk to your doctor about what you can expect.

The antibody drugs (trastuzumab, pertuzumab, and ado-trastuzumab emtansine) can cause heart damage. They can’t be given to people who already have a weak heart, so your doctor may check your heart function before giving you these drugs. If you are getting one of these drugs, you should tell your doctor right away if you have any shortness of breath, swelling of the feet or legs, or trouble with physical activities.

None of these drugs should be given to women who are pregnant because they can harm and even cause death to the fetus. Women who could become pregnant need to use effective birth control during treatment.

Everolimus (Affinitor®)

Everolimus is a type of targeted therapy that seems to help hormone therapy drugs work better in treating breast cancer that is hormone receptor-positive. It is used along with a hormone therapy drug to treat advanced breast cancer. It is meant to be used after a first hormone therapy drug stops working. Everolimus is a pill taken once a day.

Common side effects of this drug include:

  • Mouth sores
  • Diarrhea
  • Nausea
  • Fatigue
  • Feeling weak or tired
  • Low blood counts
  • Shortness of breath
  • Cough

Everolimus can also affect certain lab tests, so your doctor will check your blood work at times while you are on this drug.

For more information about targeted therapy drugs to treat breast cancer, see our document Breast Cancer.


Last Medical Review: 09/09/2014
Last Revised: 09/09/2014