Chemotherapy is a second choice for treatment of cancer. Chemotherapeutic agents are toxic chemicals that are used to kill the cancer cells. However, since all cells in the body are undergoing the exact same living processes, all chemotherapeutic agents kill normal cells as well as cancer cells. The drugs and the dose of those drugs that are used for chemotherapy are a delicate balance between killing the cancer cells and killing the normal cells of the body. Radiation is the third mode of cancer therapy.
Radiation has the potential to kill any cell in the body.
Again, the idea of radiation therapy for cancer is to localize the destructive beam to the cancer, sparing the normal cells. This can be very successful when the cancer is a solitary nodule and the radiation beam can be focused on the cancer.