Intensity-modulated radiation therapy (IMRT)
Intensity-modulated radiation therapy (IMRT) is an advanced cancer treatment technique that precisely delivers higher doses of radiation to tumors while minimizing exposure to surrounding healthy tissue. This method is particularly beneficial for treating various cancers, including those of the breast, lung, prostate, and head and neck, as well as lymphomas. IMRT allows for greater control over radiation delivery through adjustable beam intensities, enabling clinicians to customize treatment for different tumor shapes and locations, especially those located near vital organs that are challenging to reach with traditional methods.
The IMRT process begins with a comprehensive evaluation and staging imaging to map the tumor's three-dimensional shape, which informs the treatment plan. During the procedure, a linear accelerator (LINAC) directs the radiation beams, which can be varied in intensity and positioning to target the tumor effectively. Treatments are typically outpatient and last between fifteen to thirty minutes, with most patients able to drive themselves home afterward. While some temporary side effects such as fatigue and localized skin redness may occur, the overall risks to adjacent healthy structures are minimal. IMRT aims to shrink tumors and relieve symptoms, often requiring multiple treatment sessions over a period of weeks or months.
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Intensity-modulated radiation therapy (IMRT)
DEFINITION: Intensity-modulated radiation therapy (IMRT) is a cancer treatment that allows the precise delivery of higher doses of radiation to the cancer while protecting the normal tissue surrounding the tumor.
Cancers treated: Cancers of the breast, head and neck, lung, prostate, liver, cervix, colon, stomach, uterus, and brain; lymphomas
Why performed: IMRT enables radiation oncologists to deliver radiation to areas of the body that may be difficult to treat or to reach tumors near vital organs that cannot be treated surgically. Since IMRT allows higher doses of radiation to be given directly to the tumor and avoids normal tissue, there are fewer side effects than with traditional external radiation therapy.
IMRT provides a more precise, conformed radiation dose to be delivered to the tumor area by controlling the radiation beam's intensity within a given area. Radiation beams can be turned on, off, or blocked during treatment, varying the beam intensity across the targeted field. The radiation beam or beams may be moved hundreds of times, with each beam having a different intensity. Using IMRT allows lower doses of radiation to be delivered to one area of the tumor while higher doses may be delivered to another.
Patient preparation: There are no special preparations prior to IMRT treatment.
Steps of the procedure: A radiation oncologist evaluates the patient approximately one to two weeks before treatment. A staging computed tomography (CT) scan helps identify the three-dimensional shape of the tumor. This information guides the plan, dose, and shape of the radiation beam(s) for treatment. Other tests may be needed.
The radiation oncologist works with a dosimetrist, who calculates the dosage, and a medical physicist to ensure that the radiation is delivered to the exact tumor area location. A machine called a linear accelerator (LINAC) is used to direct the beam. The area where the beam will be directed is usually temporarily tattooed on the patient’s skin with ink, which will help the radiologist each time the IMRT is given to the patient. IMRT usually takes fifteen to thirty minutes.
After the procedure: IMRT is given on an outpatient basis. Patients can usually drive themselves to and from treatment. After IMRT, the patient may experience some fatigue and, depending on the area of treatment, may have some redness on the skin over the area being treated. These effects are temporary and will subside a few weeks after treatment ends. Patients may also want to discuss taking vitamin supplements with their physician.
Risks: The risks of IMRT affecting normal tissue and arteries adjacent to the tumor are minimal.
Results: IMRT aims to reduce tumor size and alleviate symptoms. Depending on the success of the results, IMRT involves multiple treatment sessions over weeks or months.
Bibliography
Chao, K. S. Clifford. Intensity Modulated Radiation Therapy for Head and Neck Cancer. Lippincott, 2003.
Chao, K. S. Clifford, et al. Practical Essentials of Intensity Modulated Radiation Therapy. 3rd ed. Lippincott, 2014.
Das, Indra J., et al. Intensity Modulated Radiation Therapy: A Clinical Overview. IOP Publishing, 2021.
"Intensity-Modulated Radiation Therapy (IMRT)." Cleveland Clinic, 1 Sept. 2022, my.clevelandclinic.org/health/treatments/17133-intensity-modulated-radiation-therapy. Accessed 20 June 2024.
"Intensity-Modulated Radiation Therapy (IMRT)." Mayo Clinic, 16 Apr. 2024, www.mayoclinic.org/tests-procedures/intensity-modulated-radiation-therapy/about/pac-20385147. Accessed 20 June 2024.
Levitt, Seymour H., et al. Technical Basis of Radiation Therapy: Practical Clinical Applications. 5th ed. Springer, 2012.
Washington, Charles M., and Dennis T. Leaver. Principles and Practice of Radiation Therapy. 5th ed. St. Mosby, 2020.
"What Is Intensity-Modulated Radiation Therapy (IMRT)?" Memorial Sloan Kettering Cancer Center, www.mskcc.org/cancer-care/diagnosis-treatment/cancer-treatments/radiation-therapy/what-imrt. Accessed 20 June 2024.