Systemic therapy is used to target cancer cells throughout the entire body, not just the breast. When this type of treatment is given after surgery to remove cancer, it is called adjuvant therapy. In some instances, it is given preoperatively to shrink a tumor, resulting in a less extensive surgery. This treatment is called neoadjuvant therapy.
The purpose of systemic therapy is to kill cancer cells that might have spread beyond the breast and to avoid metastasis in the future. Systemic therapy may include chemotherapy, hormonal therapy and the use of agents to target specific molecules involved in tumor growth.
Cancer can spread to other parts of the body through the blood vessels or lymphatic system. In early stages, these micrometastases cannot be seen on x-rays, MRI, CT or PET scans. The goal of chemotherapy is to destroy these cancer cells. In breast cancer, usually a combination of two or more chemotherapy agents is used. These cytotoxic (cell killing) medications are administered by intravenous infusion under close supervision of a medical oncologist (a doctor specializing in treatment of cancer).
In recent years medications have been developed which help minimize the undesired effects of chemotherapy. While targeting cancer cells, normal cells can also be affected. Most often the cells of the gastrointestinal tract, bone marrow, hair follicles and reproductive systems are affected. This can result in nausea, vomiting, low white blood cell count, low platelet count and fatigue. Every patient responds differently to chemotherapy, and with administration of symptom-controlling drugs, many women are able to maintain a relatively normal routine.
The hormones estrogen and progesterone can promote growth of some breast cancer cells. These cancers are called ER-positive (estrogen receptor positive) and PR-positive (progesterone receptor positive). Hormonal therapy uses medications to prevent cancer cells from growing by blocking the production of estrogen, blocking receptor sites on cancer cells or by suppressing ovarian function. Tamoxifen is frequently prescribed as an estrogen receptor blocking agent. This medication is taken daily as a pill, usually for a period of five to ten years after surgery.
A group of medications called aromatase inhibitors (e.g. Armidex, Femara and Aromasin) are used to block estrogen production in postmenopausal women. Ovarian function may need to be suppressed in premenopausal women. Several different procedures and or medications can now be used. A medical oncologist can help a patient decide on the best treatment options along with her gynecologist.
Please consult the American Cancer Society for more information on systemic therapy.