Chemotherapy refers to the use of anti-cancer drugs to kill breast cancer cells. The doctor who determines which drugs will be used, and in what dosage is known as an oncologist. Chemotherapy can be used for three major purposes:
Adjuvant therapy: The goal is to prevent or postpone cancer from coming back after the initial surgery and radiation. Even when the cancer seems to be confined to the breast and lymph glands under the arm, there is a chance that cells may have already spread to other areas that cannot be seen. Chemotherapy is given to try and kill these cells.
Neo-adjuvant therapy. Sometimes the cancer in the breast is so big that shrinking it first with chemotherapy may make it easier to do surgery.
To treat metastatic disease. If the cancer shows up in parts of the body other than the breast and lymph glands under the arm, it is called metastatic disease. Chemotherapy can be one of the main ways to kill cancer cells that have spread to other parts of the body.
When to start chemotherapy, what drugs to use, and what side effects to expect varies from woman to woman. Women should discuss this with their doctors.
Chemotherapy drugs are usually given in 2-4 week cycles, but some may be used on a weekly basis. In adjuvant and neo-adjuvant settings, they are usually given in combinations of two or more drugs. Single agent (one drug at a time) may be an option in treating breast cancer that has already spread to other areas. Although responses to combination chemotherapy are higher, toxicity is also greater as compared to single agent chemotherapy.