Chemotherapy is the use of drugs to treat cancer. Unlike radiation and surgery, which are localized treatments, chemotherapy is a systemic treatment, meaning the drugs travel throughout the whole body. In other words, chemotherapy can reach cancer cells that may have spread, or metastasized, to other areas. Chemotherapy acts on cells that divide rapidly, which includes some tumor cells. The drugs interfere with division of the cell, or the cell's method of reproduction. If the cell is unable to reproduce, it will eventually die without another cell to replace it. The net effect, then, is a decreased number of tumor cells. More than one chemotherapy drug may be given at a time. In fact, they appear to have additional effects when combined. The combination of drugs given varies according to patient diagnosis and depends on whether there has been enough time between cycles for the blood counts to recover. Multiple cycles of the drug are also given to destroy more cancer cells. Chemotherapy is used to treat many different types of cancer. The type, location and stage of the cancer, as well as your general health, will largely determine if chemotherapy is appropriate and which agents should be used.
The science of radiation oncology involves the treatment of cancer with high-energy x-rays. These x-rays cause damage to cancer cells, even cell death in some instances, which can prevent cells from reproducing. Generally, two methods are used to deliver these x-rays to the tumor: external beam irradiation and brachytherapy (radioactive implant). With external beam therapy, the treatment is given using a linear accelerator that directs the beam of irradiation to the cancer. The actual treatment is similar to taking an x-ray of the cancer. Such a treatment takes about 15 minutes to receive and is usually delivered every day for a number of weeks (the radiation oncologist determines the total number of treatments). The patient does not see or feel the radiation treatment and side effects from the treatment may develop over time, depending on the area treated. Brachytherapy or radioactive implant, meanwhile, is a technique of placing a radioactive source, usually in the form of a pellet or seed, close to the tumor. This radioactive source emits a dose of irradiation that helps kill the cancer. Brachytherapy is used for tumors in a number of sites; the most common are prostate, cervix, uterus and breast. Radiation therapy can also be used in combination with chemotherapy. The combined modalities are used to increase the potential for success and this approach is used in a number of different cancers to increase survival.