Chemotherapy is a cancer treatment using a combination of drugs in order to destroy certain cancer cells in tumors or ones that may have spread to other parts of the body. Chemotherapy is known as a systemic treatment because it is a type of treatment that affects the entire body. Chemotherapy is used when there is the possibility that cancer cells remain in the body even after other types of treatment has been performed.

The combination of drugs used in chemotherapy always varies according to the patients involved. Chemotherapy drugs are classified into different groups based on how they affect the various elements involved in breast cancer. Certain drugs like hormones can reduce the growth of cancer cells while other drugs can target the cancer cell's structure, reproductive capabilities, and DNA, among other things.

There are other types of drug therapies that target breast cancer but are not considered to be chemotherapy. Immunotherapy treatments are drug therapies that stimulate a patient's ability to increase their immune systems. Most immunotherapy drug treatments are given in conjunction with chemotherapy.

Chemotherapy that is given in combination with surgeries or radiotherapy is known as adjuvant chemotherapy. Most adjuvant chemotherapy is given after surgery or radiotherapy some month or so after the patient has recovered.

Chemotherapy is often given when the cancer is seen to be unusually aggressive. Chemotherapy can be given when cancer is found in the lymph nodes, if the tumor is particularly large, or if the cells are dividing at a high rate. Most breast cancer patients will also have the drug therapy if their cancer has a high risk of spreading to other parts of the body.

Chemotherapy for breast cancer is given as a treatment in three or four week intervals during a period of four to six months. Most chemotherapy that necessitates hospital visits consists of IV infusions that are given on an outpatient basis. Therapy is varied and depends on several factors including the severity of the cancer, the rate of division, or the patient's general health.