The use of high-energy radiation from x-rays and other sources to kill cancer cells, shrink tumors, and treat other conditions.
How it works
- At high doses, radiation therapy kills cancer cells or slows their growth by damaging their DNA.
- Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and removed by the body.
Mechanism of action
Radiation therapy does not kill cancer cells right away. It takes days or weeks of treatment before DNA is damaged enough for cancer cells to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.
Types of Radiation Therapy
There are two main types of radiation therapy, external beam and internal.
The type of radiation therapy that you may have depends on many factors, including:
- The type of cancer
- The size of the tumor
- The tumor’s location in the body
- How close the tumor is to normal tissues that are sensitive to radiation
- Your general health and medical history
- Whether you will have other types of cancer treatment
- Other factors, such as your age and other medical conditions
External Beam Radiation Therapy
- External beam radiation therapy comes from a machine that aims radiation at your cancer.
- The machine is large and may be noisy.
- It does not touch you, but can move around you, sending radiation to a part of your body from many directions.
- External beam radiation therapy is a local treatment, which means it treats a specific part of your body.
- For example, if you have cancer in your lung, you will have radiation only to your chest, not to your whole body.
Internal Radiation Therapy
- Internal radiation therapy is a treatment in which a source of radiation is put inside your body. The radiation source can be solid or liquid.
- Internal radiation therapy with a solid source is called brachytherapy. In this type of treatment, seeds, ribbons, or capsules that contain a radiation source are placed in your body, in or near the tumor. Like external beam radiation therapy, brachytherapy is a local treatment and treats only a specific part of your body.
- With brachytherapy, the radiation source in your body will give off radiation for a while.
Systemic radiation therapy
- Internal radiation therapy with a liquid source is called systemic therapy. Systemic means that the treatment travels in the blood to tissues throughout your body, seeking out and killing cancer cells. You receive systemic radiation therapy by swallowing, through a vein via an IV line, or through an injection.
- With systemic radiation, your body fluids, such as urine, sweat, and saliva, will give off radiation for a while.
Radiation-Based Drugs Emerging as Cancer Therapies
Radiopharmaceuticals deliver radiation therapy directly and specifically to cancer cells.
Radiation Therapy uses
- Radiation therapy is used to treat cancer and ease cancer symptoms.
- When used to treat cancer, radiation therapy can cure cancer, prevent it from returning, or stop or slow its growth.
- When treatments are used to ease symptoms, they are known as palliative treatments. External beam radiation may shrink tumors to treat pain and other problems caused by the tumor, such as trouble breathing or loss of bowel and bladder control. Pain from cancer that has spread to the bone can be treated with systemic radiation therapy drugs called radiopharmaceuticals.
Types of Cancer that Are Treated with Radiation Therapy
- External beam radiation therapy is used to treat many types of cancer.
- Brachytherapy is most often used to treat cancers of the head and neck, breast, cervix, prostate, and eye.
- A systemic radiation therapy called radioactive iodine, or I-131, is most often used to treat certain types of thyroid cancer.
Another type of systemic radiation therapy, called targeted radionuclide therapy, is used to treat some patients who have advanced prostate cancer or gastroenteropancreatic neuroendocrine tumor (GEP-NET). This type of treatment may also be referred to as molecular radiotherapy.
Combined radiation therapy
- For some people, radiation may be the only treatment you need. But, most often, you will have radiation therapy with other cancer treatments, such as surgery, chemotherapy, and immunotherapy. Radiation therapy may be given before, during, or after these other treatments to improve the chances that treatment will work. The timing of when radiation therapy is given depends on the type of cancer being treated and whether the goal of radiation therapy is to treat the cancer or ease symptoms.
Combined with surgery
- Before surgery, to shrink the size of the cancer so it can be removed by surgery and be less likely to return.
- During surgery, so that it goes straight to the cancer without passing through the skin. Radiation therapy used this way is called intraoperative radiation. With this technique, doctors can more easily protect nearby normal tissues from radiation.
- After surgery to kill any cancer cells that remain.
Lifetime Dose Limits
There is a limit to the amount of radiation an area of your body can safely receive over the course of your lifetime. Depending on how much radiation an area has already been treated with, you may not be able to have radiation therapy to that area a second time. But, if one area of the body has already received the safe lifetime dose of radiation, another area might still be treated if the distance between the two areas is large enough.
Glossary of Radiation Therapy Terms
This glossary provides an extensive list of terms and concepts related to radiation therapy, a medical treatment involving the use of ionizing radiation for cancer treatment and other medical conditions.
Numerical and Measurement Terms
- 4DCT: Four-dimensional computed tomography used for treatment planning.
- D50 (radiotherapy): The dose of radiation required to achieve a specified effect in 50% of irradiated cells.
- Dosimetry: The measurement of radiation dose distribution.
- Dose profile: A graphical representation of radiation dose along a line or plane.
- Monitor unit: A measure of the dose delivered during radiation therapy.
- Tissue-to-air ratio: A ratio used in dosimetry to determine radiation dose.
- Percentage depth dose curve: A graph showing the dose distribution as a function of depth in tissue.
Radiation Sources and Techniques
- Bragg peak: The peak in a depth-dose curve for charged particle radiation therapy.
- Cobalt therapy: Radiation therapy using cobalt-60 as the radiation source.
- Electron therapy: Radiation therapy using high-energy electrons.
- Henri Coutard: A pioneer in the field of radiation therapy.
- Neutron generator: A device used to produce neutrons for neutron therapy.
- Pencil-beam scanning: A precise form of radiation therapy that uses narrow beams.
- Proton computed tomography: Imaging technique using proton beams.
- Superficial X-rays: Low-energy X-rays used for treating skin cancers.
- Orthovoltage X-rays: Medium-energy X-rays used in radiation therapy.
- Plaque radiotherapy: A form of brachytherapy using a radioactive plaque.
Treatment and Techniques
- Chemoradiotherapy: A combination of chemotherapy and radiation therapy.
- Intraoperative radiation therapy: Radiation therapy delivered during surgery.
- Radiation treatment planning: The process of planning radiation therapy.
- Prophylactic cranial irradiation: Radiation therapy to prevent brain metastases.
- Dose-volume histogram: A graphical representation of radiation dose distribution in target volumes and organs at risk.
- Deep inspiration breath-hold: A technique used to minimize radiation exposure to healthy tissues.
- Oxygen enhancement ratio: A measure of the increase in radiation damage with higher oxygen levels.
- Boron neutron capture therapy: A cancer treatment using boron and neutron irradiation.
Imaging and Diagnostic Terms
- PSMA scan: Prostate-specific membrane antigen scan used in prostate cancer imaging.
- Gallium scan: Imaging technique using gallium-68 for cancer detection.
- Indium-111 WBC scan: White blood cell scan using indium-111 for infection detection.
- PET for bone imaging: Positron emission tomography used for bone imaging.
- Radionuclide therapy: Therapeutic use of radioactive materials to treat diseases.
- Bone-seeking radioisotope: Radioisotopes that target bones for imaging and therapy.
Adverse Effects and Side Effects
- Radiation burn: Skin damage caused by exposure to ionizing radiation.
- Radiation colitis: Inflammation of the colon due to radiation therapy.
- Radiation enteropathy: Damage to the intestines caused by radiation therapy.
- Radiation proctitis: Inflammation of the rectum due to radiation therapy.
- Radiation-induced lung injury: Lung damage resulting from radiation therapy.
- Side effects of radiotherapy on fertility: Effects of radiation therapy on fertility.
Specialized Techniques and Devices
- Abscopal effect: A phenomenon where radiation affects distant, non-irradiated tumors.
- Pretargeting (imaging): A technique used in molecular imaging.
- Microwave thermotherapy: A treatment method using microwaves to generate heat.
- Dose verification system: Tools and methods to verify radiation doses.
- Oncology information system: Software for managing oncology patient data.
- Diffusing alpha emitters radiation therapy: A cancer treatment using alpha-emitting radionuclides.
Organizations and Journals
- Sirtex: A company specializing in liver cancer treatments.
- Radiation oncologist: A medical professional specializing in radiation therapy.
- Radiotherapy & Oncology (journal): A scientific journal covering radiation oncology.
Historical and Miscellaneous Terms
- History of radiation therapy: A historical overview of radiation therapy.
List of Radiation oncologists (USA)
- New Hampshire
- New Jersey
- New Mexico
- New York
- North Carolina
- North Dakota
- Rhode Island
- South Carolina
- South Dakota
- West Virginia
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