Radiation treatment for cancer, or radiotherapy, uses high-energy radiation to kill malignant cancer cells by damaging their DNA, making replication impossible. Used in more than half of cancer cases, radiation may be delivered from outside the body, as in external beam radiation therapy, or from inside the body using a technique called brachytherapy. Another type of radiation treatment is systemic radiation therapy, in which a radioactive substance is carried by the bloodstream to cancerous cells. Radiation is used to kill cancer cells and shrink tumors. It may be used before, during or after cancer surgery.
The most commonly used form of radiation treatment for cancer is external beam radiotherapy. This treatment uses high-energy x-rays and gamma rays, targeted directly at the cancerous tumor from an external source. Several forms of external beam radiotherapy minimize damage to healthy tissues near the tumor. Intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT) are advanced techniques that spare healthy tissues. The machine used in all types of external beam radiotherapy aims the radiation beam precisely at the tumor without touching the patient.
External beam radiotherapy generally lasts from one to five minutes and is done over a course of two to ten weeks depending on the type of cancer and its stage of development. Therapy sessions are generally done daily for five consecutive days. The treatment itself does not hurt, but patients may experience side effects.
Proton beam radiation therapy differs from external beam radiotherapy due to its ability to concentrate the radiation's energy at a specific depth in the body. This allows a much more exacting therapy with less damage to surrounding tissue. Small, well-defined tumors can be treated using proton beam radiation. Tumors in the prostate, brain, neck and head can be targeted precisely, minimizing radiation damage to healthy tissue.
Internal radiation treatment for cancer, or brachytherapy, also uses radiation to destroy cancer cells and shrink tumors. In this form of treatment the radiation is delivered from inside the body. The source of radiation is implanted in the body using a catheter inserted into the cancerous tissues. The implants look like ribbons, wires or seeds and may be left in the body for minutes, hours, days or permanently.
Low-dose radiation implants are left in the body for up to a week, and the patient is hospitalized throughout the treatment. High-dose implants are left in for only a few minutes, and treatments are done in a series. The duration of treatment is different for each type of cancer. Permanent implants become less radioactive over time, and the oncologist will explain safety precautions to patients.
Systemic radiation treatment for cancer uses radioactive medicines that are given intravenously or orally. The medications travel through the bloodstream to the cancerous cells. Treatments are done while the patient is hospitalized, usually in a specially shielded room so others aren't exposed to the radiation. Safety precautions are outlined to protect friends and family from radiation after the treatment. Eventually, the radiation completely passes from the patient's body.