Frequently Asked Questions
- What is radiation therapy?
- When is radiation therapy used?
- What is the difference between external radiation therapy, internal radiation therapy (brachytherapy), and systemic radiation therapy? When are these types used?
- What is Image-guided radiation therapy?
- Will radiation therapy make the patient radioactive?
- How does the doctor measure the dose of radiation?
- Are there risks involved?
What is radiation therapy?
Radiation therapy (also called radiotherapy, x-ray therapy, or irradiation) is the use of a certain type of energy (called ionizing radiation) to kill cancer cells and shrink tumors. Radiation therapy injures or destroys cells in the area being treated (the �target tissue�) by damaging their genetic material, making it impossible for these cells to continue to grow and divide. Although radiation damages both cancer cells and normal cells, most normal cells can recover from the effects of radiation and function properly. The goal of radiation therapy is to damage as many cancer cells as possible, while limiting harm to nearby healthy tissue.
There are different types of radiation and different ways to deliver the radiation. For example, certain types of radiation can penetrate more deeply into the body than can others. In addition, some types of radiation can be very finely controlled to treat only a small area (an inch of tissue, for example) without damaging nearby tissues and organs. Other types of radiation are better for treating larger areas.
In some cases, the goal of radiation treatment is the complete destruction of an entire tumor. In other cases, the aim is to shrink a tumor and relieve symptoms. In either case, doctors plan treatment to spare as much healthy tissue as possible.
About half of all cancer patients receive some type of radiation therapy. Radiation therapy may be used alone or in combination with other cancer treatments, such as chemotherapy or surgery. In some cases, a patient may receive more than one type of radiation therapy.
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When is radiation therapy used?
Radiation therapy may be used to treat almost every type of solid tumor, including cancers of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin, spine, stomach, uterus, or soft tissue sarcomas. Radiation can also be used to treat leukemia and lymphoma (cancers of the blood-forming cells and lymphatic system, respectively). Radiation dose to each site depends on a number of factors, including the type of cancer and whether there are tissues and organs nearby that may be damaged by radiation.
For some types of cancer, radiation may be given to areas that do not have evidence of cancer. This is done to prevent cancer cells from growing in the area receiving the radiation. This technique is called prophylactic radiation therapy.
Radiation therapy also can be given to help reduce symptoms such as pain from cancer that has spread to the bones or other parts of the body. This is called palliative radiation therapy.
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What is the difference between external radiation therapy, internal radiation therapy (brachytherapy), and systemic radiation therapy? When are these types used?
Radiation may come from a machine outside the body (external radiation), may be placed inside the body (internal radiation), or may use unsealed radioactive materials that go throughout the body (systemic radiation therapy). The type of radiation to be given depends on the type of cancer, its location, how far into the body the radiation will need to go, the patient's general health and medical history, whether the patient will have other types of cancer treatment, and other factors.
Most people who receive radiation therapy for cancer have external radiation. Some patients have both external and internal or systemic radiation therapy, either one after the other or at the same time.
External radiation therapy usually is given on an outpatient basis; most patients do not need to stay in the hospital. External radiation therapy is used to treat most types of cancer, including cancer of the bladder, brain, breast, cervix, larynx, lung, prostate, and vagina. In addition, external radiation may be used to relieve pain or ease other problems when cancer spreads to other parts of the body from the primary site.
Intraoperative radiation therapy (IORT) is a form of external radiation that is given during surgery. IORT is used to treat localized cancers that cannot be completely removed or that have a high risk of recurring (coming back) in nearby tissues. After all or most of the cancer is removed, one large, high-energy dose of radiation is aimed directly at the tumor site during surgery (nearby healthy tissue is protected with special shields). The patient stays in the hospital to recover from the surgery. IORT may be used in the treatment of thyroid and colorectal cancers, gynecological cancers, cancer of the small intestine, and cancer of the pancreas. It is also being studied in clinical trials (research studies) to treat some types of brain tumors and pelvic sarcomas in adults.
Prophylactic cranial irradiation (PCI) is external radiation given to the brain when the primary cancer (for example, small cell lung cancer) has a high risk of spreading to the brain.
Internal radiation therapy (also called brachytherapy) uses radiation that is placed very close to or inside the tumor. The radiation source is usually sealed in a small holder called an implant. Implants may be in the form of thin wires, plastic tubes called catheters, ribbons, capsules, or seeds. The implant is put directly into the body. Internal radiation therapy may require a hospital stay.
Internal radiation is usually delivered in one of two ways, each of which is described below. Both methods use sealed implants.
Interstitial radiation therapy is inserted into tissue at or near the tumor site. It is used to treat tumors of the head and neck, prostate, cervix, ovary, breast, and perianal and pelvic regions. Some women treated with external radiation for breast cancer receive a �booster dose� of radiation that may use interstitial radiation or external radiation.
Intracavitary or intraluminal radiation therapy is inserted into the body with an applicator. It is commonly used in the treatment of uterine cancer. Researchers are also studying these types of internal radiation therapy for other cancers, including breast, bronchial, cervical, gallbladder, oral, rectal, tracheal, uterine, and vaginal.
Systemic radiation therapy uses radioactive materials such as iodine 131 and strontium 89. The materials may be taken by mouth or injected into the body. Systemic radiation therapy is sometimes used to treat cancer of the thyroid and adult non-Hodgkin lymphoma. Researchers are investigating agents to treat other types of cancer.
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What is Image-guided radiation therapy?
Image-guided radiation therapy (IGRT) is the process of frequent two and three-dimensional imaging, during a course of radiation treatment, used to direct radiation therapy utilizing the imaging coordinates of the actual radiation treatment plan. The patient is localized in the treatment room in the same position as planned from the reference imaging dataset. An example of Three-dimensional (3D) IGRT would include localization of a cone-beam computed tomography (CBCT) dataset with the planning computed tomography (CT) dataset from planning. Similarly Two-dimensional (2D) IGRT would include matching planar kilovoltage (kV) radiographs fluoroscopy or megavoltage (MV) images with digital reconstructed radiographs (DRRs) from the planning CT.
This process is distinct from the use of imaging to delineate targets and organs in the planning process of radiation therapy. However, there is clearly a connection between the imaging processes as IGRT relies directly on the imaging modalities from planning as the reference coordinates for localizing the patient. The variety of image gathering hardware used in planning includes Computed Tomography(CT), Magnetic Resonance Imaging (MRI), and Positron Emission Tomography (PET) among others. Through advancements in imaging technology, combined with a further understanding of human biology at the molecular level, the impact of IGRT on radiotherapy treatment continues to evolve.
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Will radiation therapy make the patient radioactive?
Cancer patients receiving radiation therapy are often concerned that the treatment will make them radioactive. The answer to this question depends on the type of radiation therapy being given.
External radiation therapy will not make the patient radioactive. Patients do not need to avoid being around other people because of the treatment.
Internal radiation therapy (interstitial, intracavitary, or intraluminal) that involves sealed implants emits radioactivity, so a stay in the hospital may be needed. Certain precautions are taken to protect hospital staff and visitors. The sealed sources deliver most of their radiation mainly around the area of the implant, so while the area around the implant is radioactive, the patient's whole body is not radioactive.
Systemic radiation therapy uses unsealed radioactive materials that travel throughout the body. Some of this radioactive material will leave the body through saliva, sweat, and urine before the radioactivity decays, making these fluids radioactive. Therefore, certain precautions are sometimes used for people who come in close contact with the patient. The patient's doctor or nurse will provide information if these special precautions are needed.
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How does the doctor measure the dose of radiation?
The amount of radiation absorbed by the tissues is called the radiation dose (or dosage). Before 1985, dose was measured in a unit called a �rad� (radiation absorbed dose). Now the unit is called a gray (abbreviated as Gy). One Gy is equal to 100 rads; one centigray (abbreviated as cGy) is the same as 1 rad.
Different tissues can tolerate various amounts of radiation (measured in centigrays). For example, the liver can receive a total dose of 3,000 cGy, while the kidneys can tolerate only 1,800 cGy. The total dose of radiation is usually divided into smaller doses (called fractions) that are given daily over a specific time period. This maximizes the destruction of cancer cells while minimizing the damage to healthy tissue.
The doctor works with a figure called the therapeutic ratio. This ratio compares the damage to the cancer cells with the damage to healthy cells. Techniques are available to increase the damage to cancer cells without doing greater harm to healthy tissues. These techniques are discussed in Questions 8, 9, and 15.
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Are there risks involved?
Like many other treatments for disease, there are risks for patients who are receiving radiation therapy. The brief high doses of radiation that damage or destroy cancer cells also can hurt normal cells. When this happens, the patient has side effects. The risk of side effects is usually less than the benefits of killing cancer cells.
Your doctor will not advise you to have any treatment unless the benefits -control of disease and relief from symptoms -are greater than the known risks. Although it will be many years before scientists know all of the possible risks of radiation therapy, they now know that it can control cancer.
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Here are some words and phrases that you may hear from your Oregon Urology Institute Radiation team:
A treatment method used in addition to the primary therapy. Radiation therapy often is used as an adjuvant to surgery.
Loss of feeling or sensation resulting from the use of certain drugs or gasses.
A medicine to prevent or relieve nausea or vomiting.
A growth that is not a cancer and does not spread to other parts of the body.
Treatment by stimulation of the body's immune defense system.
The removal of a sample of tissue to see whether cancer cells are present.
Internal radiation treatment achieved by implanting radioactive material directly into the tumor or very close to it. Sometimes called "internal radiation therapy."
A general term for more than 100 diseases that have uncontrolled, abnormal growth of cells that can invade and destroy healthy tissues.
A thin, flexible tube through which fluids enter or leave the body.
Treatment with anticancer drugs.
A radioactive substance used as a radiation source to treat cancer.
Dietitian (also registered dietician):
A professional who plans diet programs for proper nutrition.
A person who plans and calculates the proper radiation dose for treatment.
A stream of particles that produces high-energy radiation to treat cancer.
Radiation therapy that uses a machine located outside of the body to aim high-energy rays at cancer cells.
A chemical applied to the teeth to prevent tooth decay.
High-energy rays that come from a radioactive source such as cobalt-60.
A measurement of absorbed radiation dose. 1 Gray = 100 rads.
High dose rate remote brachytherapy:
A type of internal radiation in which each treatment is given in a few minutes while the radioactive source is in place. The source of radioactivity is removed between treatments. Also known as high dose rate remote radiation therapy.
Division of the total dose of radiation into smaller doses that are given more than once a day.
A type of external radiation used to deliver a large dose of radiation therapy to the tumor bed and surrounding tissue at the time of surgery.
Cancerous (see cancer).
A doctor who specializes in using chemotherapy to treat cancer.
The spread of a cancer from one part of the body to another. Cells in the second tumor are like those in the original tumor.
A doctor who specializes in treating cancer.
Treatment to relieve, rather than cure, symptoms caused by cancer. Palliative care can help people live more comfortably.
A health professional trained in the use of treatments such as exercise and massage.
Special blood cells that help stop bleeding.
An artificial replacement of a part of the body.
Short form for "radiation absorbed dose;" a measurement of the amount of radiation absorbed by tissues (100 rad = 1 Gray).
Energy carried by waves or a steam of particles.
A doctor who specializes in using radiation to treat cancer.
A person trained to ensure that the radiation machine delivers the right amount of radiation to the treatment site.
A person with special training who runs the equipment that delivers the radiation.
The use of high-energy penetrating rays or subatomic particles to treat disease. Types of radiation include x-ray, electron beam, alpha and beta particles, and gamma rays. Radioactive substances include cobalt, radium, iridium, and cesium. (See also gamma rays, brachytherapy, teletherapy, and x-ray.)
A physician with special training in reading diagnostic x-rays and performing specialized x-ray procedures.
See radiation therapy.
A process involving special x-ray pictures that are used to plan radiation treatment so that the area to be treated is precisely located and marked.
Treatment port or field:
The place on the body at which the radiation beam is aimed.
An abnormal mass of tissue. Tumors are either benign or malignant.
White blood cells:
The blood cells that fight infection.
High-energy radiation that can be used at low levels to diagnose disease or at high levels to treat cancer.
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