Radiation Therapy Overview
Radiation describes the way energy moves from one place to another. Sometimes this is in the form of particles such as protons, while other times it is in the form of waves like x-rays or visible light. The various types of radiation are grouped according to how much energy they contain. Low energy radiation, like radio waves and heat, is known as non-ionizing radiation. High energy radiation, such as ultraviolet (UV) light from the sun and x-rays, is known as ionizing radiation because it has enough energy to break chemical bonds and knock electrons (negatively charged particles) out of atoms. When these changes take place in cells, it can sometimes cause enough damage to kill the cells. As a result, such high-energy x-rays or other particles can be used to destroy cancer cells in a treatment called radiation therapy.
Types of Radiation Therapy
External-beam radiation therapy
This is the most common type of radiation treatment, and it involves giving radiation from a machine located outside the body. It can treat large areas of the body, if necessary. The machine typically used to create the radiation beam is called a linear accelerator or linac. Computers with special software are used to adjust the size and shape of the beam and to direct it to target the tumor while avoiding the healthy tissue that surrounds the cancer cells. External-beam radiation therapy does not make you radioactive.
Types of external-beam radiation therapy include:
Internal radiation therapy
This type of radiation treatment, also known as brachytherapy, involves placing radioactive material into the cancer itself or into the tissue surrounding it. These radioactive implants may be permanent or temporary and may require a hospital stay. Permanent implants are tiny steel seeds (capsules) about the size of a grain of rice that contain radioactive material and are placed inside the body at the tumor site. The seeds deliver most of the radiation around the area of the implant; however, some radiation can be emitted (released) from the patient’s body. This means the patient needs to take special precautions to protect others from radiation exposure while the seeds are still active. Over time, the implant loses its radioactivity, but the inactive seeds remain in the body.
For temporary implants, the radiation is delivered through needles, catheters (tubes that carry fluid in or out of the body), or specialized applicators and kept in the body for a specific amount of time, from a few minutes to a few days. Most temporary implant procedures deliver radiation for just a few minutes. If temporary implants are used for more time, the patient remains in a private room while the implants are in place to limit others’ exposure to the radiation.
The side effects of radiation therapy depend on the treatment dose and the part of the body that is being treated.
Radiation therapy may also cause a decrease in the number of white blood cells (cells that help protect the body against infection).
Before you undergo external beam radiation therapy, your health care team guides you through a planning process to ensure that radiation reaches the precise spot in your body where it’s needed. Planning typically includes:
After the planning process, your radiation therapy team decides what type of radiation and what dose you’ll receive based on your type and stage of cancer, your general health, and the goals for your treatment. The precise dose and focus of radiation beams used in your treatment is carefully planned to maximize the radiation to your cancer cells and minimize the harm to surrounding healthy tissue.
Radiation therapy typically takes treatment sessions five days a week for one to 10 weeks. The total number of treatments depends on the size and type of cancer. Each session usually takes about 10 to 30 minutes. Often, the individual is given each weekend off from therapy, which helps with the restoration of normal cells.
At each session, you will lie on the treatment table, and your team will position you and apply the same types of cushions and restraints used during your initial radiation simulation. Protective covering or shields may also be positioned on or around you to protect other body parts from unnecessary radiation.
Radiation therapy involves the use of a linear accelerator machine, which directs radiation at the appropriate spot. The machine may move around the table in order to direct the radiation at the appropriate angles. The machine may also make a buzzing sound, which is perfectly normal.
You should feel no pain during this test. You will also be able to communicate with your team via the room’s intercom, if necessary. Your doctors will be nearby in an adjacent room, monitoring the test.