What is Radiation Therapy?
All cells grow and divide to form new cells. But cancer cells grow and divide faster than the normal cells around them and invade other tissues. Radiation therapy uses high-energy radiation to shrink tumors and kill cancer cells, thus preventing the cells from growing, dividing, and spreading.
Also referred to as radiotherapy, irradiation, or x-ray therapy, radiation therapy is one of the most common treatments for cancer. Unlike chemotherapy, which exposes the whole body to cancer-fighting drugs, radiation therapy is usually applied locally, affecting only the part of the body being treated and limiting harm to nearby healthy tissue.
What Type of Radiation Therapy is Best?
Deciding which type of radiation to use depends upon the kind of cancer you have and where it is in your body. Discuss with your radiation oncologist which type of treatment plan is right for you.
Frequently Asked Questions (FAQ)
"Radiation Therapy and You," a publication by the National Cancer Institute
Types of Radiation Therapy
Radiation may be delivered by a machine outside the body (external-beam radiation therapy), or may come from radioactive material placed in the body near cancer cells (internal radiation therapy, also called brachytherapy). Oncologists may also prescribe a combination of radiation therapies to treat a patient's cancer. And radiation can be given alone or used with other treatments, such as surgery or chemotherapy. In fact, certain drugs are known to be radiosensitizers. This means they can actually make the cancer cells more sensitive to radiation, which allows the radiation to better kill cancer cells.
About half of all cancer patients receive some type of radiation therapy during the course of their treatment.
External Beam Radiation Therapy
External radiation (or external beam radiation) uses a machine to direct high-energy rays from outside the body into the tumor, while minimizing radiation exposure to nearby healthy tissue. Scheduled as a series of outpatient visits, external radiation therapy is typically repeated over a period of many weeks.
Valley Medical Center employs a state-of-the-art, 3D treatment machine called a linear accelerator that uses image-guidance and x-ray technology to precisely locate tumors in real time. This is critically important since tumors can move—as a result of breathing or due to shifting caused by weight loss or other physical changes over the course of treatment. In addition, the linear accelerator is capable of mapping irregularly shaped tumors and varying the intensity and direction of beams of radiation to destroy cancerous cells and exclude healthy tissue.
There are a number of treatment plan styles available for external radiation. Selection depends upon tumor location, shape, size, proximity to organs and other factors. Discuss with your radiation oncologist which type of treatment plan is right for you.
- 2-Dimensional Radiation Therapy
- The simplest treatment plan, where the tumor is easy to get to and the exact area where the radiation beam is aimed—called a "port" or "treatment field"—is limited to one or two fields.
- Three Dimensional Conformal Radiation Therapy (3D-CRT)
- This uses computers to precisely design a plan based on the size, shape and location of the tumor while limiting the radiation dose delivered to sorrounding normal tissue. Other special imaging tests, such as CT, MRI or PET scans, may also be used to help design this plan.
- Intensity Modulated Radiation Therapy (IMRT)
- IMRT allows for the radiation dose to conform more precisely to the three-dimensional (3-D) shape of the tumor by modulating, or controlling, the intensity of the radiation beam in short bursts. IMRT also can also focus higher radiation doses within the tumor and minimize the dose to surrounding normal critical structures. Treatment is carefully planned by using 3-D computed tomography (CT) or magnetic resonance (MRI) images of the patient in conjunction with computerized dose calculations to determine the dose intensity pattern that will best conform to the tumor shape. Typically, combinations of multiple intensity-modulated fields coming from different beam directions produce a custom-tailored radiation dose that maximizes radiation delivered to the tumor and minimizes the dose to adjacent normal tissues. This allows for higher and more effective radiation doses directed at tumors with fewer side effects compared with conventional radiotherapy techniques. IMRT has been shown to reduce treatment related side effects.
- Volumetric Modulated Arc Therapy (VMAT)
- VMAT is an arc therapy technique that establishes new standards for radiation therapy treatment speed and dose reduction to the patient. With VMAT, single or multiple radiation beams sweep in uninterrupted arc(s) around the patient, dramatically speeding treatment delivery. Doctors can use VMAT with complete or partial arc(s) to reduce treatment times to as few as two minutes from the eight to twelve minutes required for “conventional” radiation therapy.
- Image Guided Radiation Therapy (IGRT)
- IGRT is the use of frequent imaging immediately before and during a course of radiation therapy to improve the precision and accuracy of delivery. Using specialized computer software, these images are then compared to the images taken during simulation. Any necessary adjustments are then made to the patient's position and/or radiation beams in order to more precisely target radiation at the tumor and avoid healthy surrounding tissue. Computed tomography (CT) and x-ray imaging may be used for IGRT.
- Electron Treatments
- Electrons are used in radiation therapy for superficial malignant and benign tumors such as skin cancer, scars or tumors found just below the skin surface. They release their energy near the skin and therefore tend not to penetrate deeper normal tissues below the skin’s surface.
- Stereotactic Radiosurgery (SRS) or Stereotactic Body Radiation Therapy (SBRT)
- SRS directs high doses of radiation in precisely focused beams (on a sub millimeter scale) to treat tumors of the brain, spine and other areas of the body. A neurosurgeon, physicist and the radiation oncologist work together to plan and deliver treatment. Treatment is shorter, delivered in a single dose or over 5 days. With SRS to the brain, the patient is fitted with a face mask or halo to help keep the head perfectly still during treatment. SRS can also be used to treat cancers of the lung, liver, pancreas, prostate and head and neck.
- Treatment with stereotactic radiosurgery is offered on-site and off-site through our association with University of Washington. Gammaknife and Cyberknife are two common brand name machines utilized to deliver this type of radiation therapy. Valley Medical Center uses Brainlab equipment. For additional questions regarding this type of treatment, consult your radiation oncologist.
Internal Radiation Therapy
Internal radiation (also called brachytherapy [brake-ee-THER-uh-pee]) uses a radioactive source in the form of a wire, seed, pellet, or balloon that’s called an implant. The implant is put inside the body in or near the tumor. The radiation from the implant travels only a short distance, so it has very little effect on normal body tissues. In some cases, patients may need to stay in the hospital while getting internal radiation.
Sometimes, after a tumor has been removed by surgery, radioactive implants are put into the area where the tumor was to kill any cancer cells that may still be there.
Implants may either be left in the patient as a permanent implant or they may be removed after a certain amount of time.
There are two types of brachytherapy, high dose and low dose. Low dose brachytherapy consists of low dose radioactive seeds permanently placed inside an organ. This is often used for prostate cancer. High dose brachytherapy involves the delivery of radiation through a temporarily placed applicator, such as a catheter. This type is often used for cervical cancer. Brachytherapy can be given alone or in conjunction with external beam radiation therapy. Your radiation oncologist will be able to provide consultation regarding this treatment here at Valley Medical Center and referral to appropriate specialist for the delivery of the treatment. Learn more about brachytherapy in the health library.
Learn more about brachytherapy in the health library.