Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. X-rays, gamma rays, and charged particles are types of radiation used for cancer treatment. Radiation therapy kills cancer cells by damaging its DNA either directly or creating charged particles (free radicals) within the cells that can in turn damage the DNA. When the DNA of cancer cells is damaged beyond repair, the cancer cells stop dividing or die. After damaged cells die, they are broken down and eliminated by the body’s natural processes. There are two main types of radiation therapy: external beam and internal.
External beam radiation therapy (ERBT) comes from a machine that aims radiation at your cancer. It does not touch you, but can move around you, sending radiation to a part of your body from many directions. ERBT is a local treatment, meaning it treats a specific part of your body. There are several different types of external beam radiation therapy.
Three-dimensional conformal radiation therapy (3D-CRT) uses images from CT, MRI, and PET scans to precisely plan the treatment area through a process called simulation. A computer program is used to analyze the images and to design radiation beams that conform to the shape of the tumor. The precise shaping makes it possible to use higher doses of radiation to the tumor while sparing normal tissue.
Intensity Modulated Radiation Therapy (IMRT) is a type of 3-D conformal radiation therapy that uses CT scans or other three-dimensional images to build the treatment plan for the precise delivery of radiation. Like 3-D conformal radiation, radiation beams are aimed at the tumor from several directions, however, IMRT uses many smaller beams than 3-D conformal, and the strength of the beams in some areas can be changed to give higher doses to certain parts of the tumor. This enables a maximum dose to the tumor while minimizing the amount of radiation distributed to the surrounding healthy tissues.
Image-guided radiation therapy (IGRT) combines three-dimensional images, such as CT scans, with the precise technology of Intensity Modulated Radiation Therapy (IMRT) to pinpoint and treat cancerous tumors. During treatment, you will have repeated scans, such as CT, MRI, or PET scans, which are processed by computers to detect changes in the tumor’s size and location. The repeated imaging allows for your position or the radiation dose to be adjusted during treatment if needed. These adjustments can improve the accuracy of treatment and help spare normal tissue. IGRT is used to treat tumors in areas of the body that are prone to movements, such as the lungs, liver, and prostate gland, as well as tumors located close to critical organs and tissues.
Stereotactic radiosurgery isn’t really a surgery, but rather the use of focused, high-energy beams to treat small tumors with well-defined edges in the brain and central nervous system. It may be an option if surgery is too risky due to your age or other health problems or if the tumor cannot safely be reached with surgery. In SRS, many small beams of radiation are aimed at the tumor from different directions. Each beam has very little effect on the tissue it passes through, but a precisely targeted dose of radiation is delivered to the site where all the beams come together.GammaKnife and CyberKnife® are two common types of stereotactic radiosurgery.
Stereotactic Body Radiotherapy (SBRT) is an advanced type of non-surgical radiation technology used to treat body tumors in locations such as the lung, liver, abdomen, spine, prostate, head, and neck.
Stereotactic Radiation Therapy (SRT) is a type of external radiation therapy that uses special equipment to position the patient and precisely deliver radiation to a tumor. The total dose of radiation is divided into several smaller doses given over several days. Stereotactic radiation therapy is used to treat brain tumors and other brain disorders.
Internal radiation therapy, more commonly called brachytherapy, involves placing a temporary or permanent radioactive implant inside your body, in or near the tumor. The implant could be in the form of seeds, balloons, tubes, capsules, ribbons, wires, pellets, or needles. Most brachytherapy is put in place through a catheter, which is a small, stretchy tube. Sometimes, it is put in place through a larger device called an applicator. The way the brachytherapy is put in place depends on your type of cancer. Your doctor will place the catheter or applicator into your body before you begin treatment.
Brachytherapy makes it possible to position a higher total dose of radiation in a smaller area than what can be achieved with external beam radiation, resulting in less radiation exposure to surrounding healthy tissue or tissues that could be very sensitive to radiation. The amount of time the implants are in place varies by the patient and the type of cancer. Some patients have implants that are left in place for only a few minutes or a few days (high-dose rate brachytherapy), while others have implants that are left in place to slowly break down on their own (low-dose rate brachytherapy).
High-dose rate (HDR) brachytherapy delivers high-doses of radiation to the tumor area from within the body or on the surface of the skin. It is administered through an applicator tube or thin catheter that is inserted into the body or through an applicator that sits on top of the skin.
This process delivers radiation for several minutes to the specific area where the cancer is located, sparing surrounding tissue. The radiation is removed from the body, unlike low-dose brachytherapy which may stay implanted.