Chemotherapy is the terminology given in the form of medical treatment which is given to cancer patients. The drugs are called as chemotherapeutic agents/drugs. It is usually given in the intravenously (blood administration), also given by mouth (oral pills), intramuscularly, or directly into the CSF via spine or ventricles. A single chemotherapeutic agent may be used or a combination of many drugs may be used at the same time or at different times.

Broadly chemotherapy may be classified based on -

1. Intent of Treatment

Curative Chemotherapy - Chemotherapy when given with a curative intent is called as curative chemotherapy. It is usually given in the early stages of cancer.
Palliative chemotherapy - It is a chemotherapy given to the patient, when the disease is in stage IV, with an intent to improve the symptoms & improve the quality of life.

2. If given before surgery or after surgery

Neo-adjuvant Chemotherapy - Chemotherapy which is given before surgery. The benefit of providing chemotherapy prior to surgery is that it enables large cancers (known as locally advanced cancers) to shrink down to sizes that can be later removed through less-extensive surgery. It allows doctors to monitor the cancer's response to drugs. The drugs used are mostly the same as used in adjuvant therapy. Neo-adjuvant therapy also enables surgical removal of only the affected tissue, and not the entire breast.
Adjuvant Chemotherapy - Chemotherapy which is given after surgery. It is given with an intent to kill the cancer cells present in the blood circulation in the body. Chemotherapy helps to prevent cancer from coming back by killing these cells.

3. If given when patient is receiving radiation therapy

Concurrent Chemotherapy - Chemotherapy which is given when the patient receives radiation therapy. It is usually given once in a week, while the patient receives radiation therapy on a daily basis

Administration of Chemotherapy

Chemotherapy drugs are usually given in two-four week cycles, but may be given on a weekly basis. Patients may receive treatment over a few hours or overnight hospital admission, or in pill form. Chemotherapy drugs are mostly given in combinations of two or more drugs during adjuvant and neo-adjuvant therapies.

Doctor will also perform regular blood tests to monitor counts of white blood cells, red blood cells and platelets. Injections and blood transfusions (in case of platelets) are given to bring the counts back to the normal range.