Medication

The most important advances in the cure of breast cancer have come through the use of drug therapy, also called systemic therapy. Surgery and radiation therapy are effective for treating tumors confined to the breast but not for cancer cells that have spread or are at risk of spreading. In such cases, drug therapy is needed.

Drugs Used for Breast Cancer

• Chemotherapy. Chemotherapy drugs are "cytotoxic" (cell-killing) drugs. They are given orally or by injection. They work systemically by killing cancer cells throughout the body. (Unfortunately, they also kill normal cells, which accounts for many of their side effects.) Chemotherapy is always used for advanced breast cancer, but may also be used to treat types of early-stage breast cancer.
• Hormone Therapy. The goal of hormone therapy is to prevent estrogen from stimulating breast cancer cells. It is recommended for women whose breast cancers are hormone-receptor positive (either estrogen or progesterone), regardless of the size of the tumor and whether or not it has spread to the lymph nodes. Like chemotherapy, hormone therapy works systemically.
• Targeted Therapy. Newer biologic drugs target specific proteins involved in cancer. Because they do not work as systemically as chemotherapy or hormone therapy drugs, they tend to cause fewer widespread side effects. Currently, the monoclonal antibody trastuzumab (Herceptin) and the kinase inhibitor lapatinib (Tykerb) are the two targeted therapies approved for breast cancer. These drugs target the HER2/neu protein and are used to treat HER2-positive breast cancers. Bevacizumab (Avastatin) is a monoclonal antibody that targets vascular endothelial growth factor (VEGF), a protein involved in tumor blood vessel formation (angiogenesis). It is being studied in clinical trials for treatment of metastatic breast cancer.

Considerations for Drug Therapies

• Primary therapy for patients for whom surgery or radiation therapy is not appropriate.
• Neoadjuvant therapy (before surgery or radiation) to shrink tumors to a size that can be treated with local therapy.
• Adjuvant therapy (following surgery or radiation) to reduce the risk of cancer recurrence.

For metastatic cancer, drugs are used not to cure but to improve quality of life and prolong survival.

Review Date: 12/21/2006
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

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