Breast Cancer

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Treating Breast Cancer TOPICS

Targeted therapy for breast cancer

As researchers have learned more about the gene changes in cells that cause cancer, they have been able to develop newer drugs that specifically target these changes. These targeted drugs work differently from standard chemotherapy (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, call us with the names of the medicines you’re taking.

Drugs that target the HER2/neu protein

In about 1 in 5 patients with breast cancer, the cancer cells have too much of a growth-promoting protein known as HER2/neu (or just HER2) on their surface. Breast cancers with too much of this protein tend to grow and spread more aggressively without special treatment. A number of drugs have been developed that target this protein:

  • Trastuzumab (Herceptin)
  • Pertuzumab (Perjeta®)
  • Ado-trastuzumab emtansine (Kadcyla)
  • Lapatinib (Tykerb)

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 chemo therapy 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. Discuss what you can expect with your doctor.

Some women do develop heart damage during or after treatment with the antibody drugs (trastuzumab, pertuzumab, and ado-trastuzumab emtansine). This can lead to a problem called congestive heart failure. For most (but not all) women, this effect lasts a short time and gets better when the drug is stopped. The risk of heart problems is higher when if these drugs are given with certain chemo drugs that also can cause heart damage, such as doxorubicin (Adriamycin) and epirubicin (Ellence). Because these drugs can cause heart damage, doctors often check your heart function (with an echocardiogram or a MUGA scan) before treatment, and check it again every few months while you are taking the drug. Major symptoms of congestive heart failure are shortness of breath, leg swelling, and severe fatigue. Let your doctor know if you develop any of these symptoms.

Lapatinib can cause severe diarrhea, so it is very important to let your health care team know about any changes in bowel habits as soon as they happen. It can also cause something called hand-foot syndrome, in which that hands and feet become sore and red, and may blister and peel.

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.

Drugs that help hormone therapy drugs work better

Palbociclib (Ibrance®) is a drug that can be used along with an aromatase inhibitor to treat women with advanced hormone receptor-positive breast cancer. This drug blocks proteins in the cell called cyclin-dependent kinase (CDK) 4 and CDK6. In breast cancer cells that are hormone receptor positive, blocking these proteins helps stop the cells from dividing to make new cells. This slows cancer growth.

Palbociclib is a pill that is taken once a day for 3 weeks at a time, with a week off before starting again. It is approved to treat advanced hormone receptor−positive, HER2−negative, breast cancer in women who have gone through menopause.

Side effects tend to be mild and include low red blood cell counts (anemia), fatigue, nausea, mouth sores, hair loss, and diarrhea. Severe low white blood cell counts can also occur, which increase the risk of serious infection.

Everolimus (Afinitor®) is a drug that can be used along with a hormone therapy drug to treat women with advanced hormone receptor-positive breast cancer. This targeted therapy drug blocks mTOR, a protein in cells that normally promotes their growth and division. By blocking this protein, everolimus can help stop cancer cells from growing. Everolimus may also stop tumors from developing new blood vessels, which can help limit their growth. In treating breast cancer, this drug seems to help hormone therapy drugs work better.

Everolimus is a pill taken once a day.

This drug is approved to treat advanced hormone receptor−positive, HER2−negative, breast cancer in women who have gone through menopause. It is meant to be used with exemestane (Aromasin) in these women if their cancers have grown while they were being treated with either letrozole or anastrozole (or the cancer started growing shortly after treatment with these drugs was stopped). This approval was based on a study that showed that giving everolimus with exemestane was better than exemestane alone in shrinking tumors and stopping their growth in post-menopausal women with hormone receptor−positive, HER2−negative breast cancer that had stopped responding to letrozole or anastrozole.

Common side effects of this drug include mouth sores, diarrhea, nausea, fatigue, feeling weak or tired, low blood counts, shortness of breath, and cough. Everolimus can also increase blood lipids (cholesterol and triglycerides) and blood sugars, so your doctor will check your blood work periodically while you are on this drug. It can also increase your risk of serious infections, so your doctor will watch you closely for infection while you are on treatment.

Everolimus is also being studied for use for earlier stage breast cancer, with other hormone therapy drugs, and combination with other treatments. This is discussed further in “What’s new in breast cancer research and treatment?

More information about monoclonal antibodies can be found in Cancer Immunotherapy.

For more information about targeted therapy drugs, see Targeted Therapy.

Last Medical Review: 09/25/2014
Last Revised: 02/22/2016