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 drugs. They often have different (and less severe) side effects. They are most often used along with chemotherapy at this time.

Drugs that target the HER2/neu protein

Trastuzumab (Herceptin): Trastuzumab is a type of drug known as a monoclonal antibody -- a man-made version of a very specific immune system protein. It attaches to a growth-promoting protein known as HER2/neu (or just HER2), which is present in larger than normal amounts on the surface of the breast cancer cells in about 1 of 5 patients. Breast cancers with too much of this protein tend to grow and spread more aggressively. Trastuzumab can help slow this growth and may also stimulate the immune system to more effectively attack the cancer.

Trastuzumab is given as an injection into a vein (IV), usually once a week or as a larger dose every 3 weeks. The optimal length of time to give it is not yet known.

Trastuzumab can be used (along with chemotherapy) as adjuvant therapy for HER2-positive cancers to reduce the risk of recurrence when the tumor is larger than 1 cm across or when the cancer has spread to the lymph nodes. Using trastuzumab along with chemotherapy has become standard adjuvant treatment for these cancers.

Trastuzumab can also shrink some HER2-positive advanced breast cancers that return after chemotherapy or continue to grow during chemotherapy. Treatment that combines trastuzumab with chemotherapy may work better than chemotherapy alone in some patients.

Compared with chemotherapy drugs, the side effects of trastuzumab are relatively mild. They may include fever and chills, weakness, nausea, vomiting, cough, diarrhea, and headache. These side effects occur less often after the first dose.

A more serious potential side effect is heart damage leading to a problem called congestive heart failure. For most (but not all) women, this effect has been temporary and has improved when the drug is stopped. The risk of heart problems is higher when trastuzumab is given with certain chemotherapy drugs such as doxorubicin (Adriamycin) and epirubicin (Ellence). Major symptoms of congestive heart failure are shortness of breath and severe fatigue. Women having these symptoms should call their doctor right away.

Lapatinib (Tykerb): Lapatinib is another drug that targets the HER2 protein. This drug is given as a pill, most often along with the chemotherapy drug capecitabine (Xeloda). It is used in women with advanced HER2-positive breast cancer that is no longer helped by chemotherapy and trastuzumab. It is also being studied as an adjuvant therapy in HER2-positive patients, but at this time is only used for advanced breast cancer.

The most common side effects of this drug include diarrhea, nausea, vomiting, rash, and hand-foot syndrome, which may include numbness, tingling, redness, swelling, and discomfort in the hands and feet. Diarrhea is common and can be severe, so it is very important to let your health care team know about any changes in bowel habits as soon as they happen.

In rare cases lapatinib may cause liver problems or a decrease in heart function (that can lead to shortness of breath), although this seems to go away once treatment is finished.

Drugs that target new tumor blood vessels (angiogenesis)

Tumors need to develop and maintain new blood vessels in order to grow. Drugs that target these blood vessels are proving to be helpful against a variety of cancers, including breast cancer.

Bevacizumab (Avastin) is a monoclonal antibody that may be used in patients with metastatic breast cancer. This antibody is directed against vascular endothelial growth factor (VEGF), a protein that helps tumors form new blood vessels.

Bevacizumab is given by intravenous (IV) infusion. It is most often used in combination with the chemotherapy drug paclitaxel (Taxol).

Rare, but possibly serious side effects include bleeding, holes forming in the colon (requiring surgery to correct), and slow wound healing.

More common side effects include high blood pressure, tiredness, blood clots, low white blood cell counts, headaches, mouth sores, loss of appetite, and diarrhea. High blood pressure is very common, so it very important that your doctor watches your blood pressure carefully during treatment.

Last Medical Review: 09/04/2008
Last Revised: 09/04/2008