Radiation therapy

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Radiation therapy utilizes ionizing radiation to treat malignant and benign diseases. It has become a standard of care for treating many types of cancer. Current medical practice uses radiation therapy in about half of all newly diagnosed cancer cases. Radiation therapy works by exploiting radiobiological differences between cancer and normal cells/tissues, and by depositing radiation dose in cancer tumours while keeping doses to surrounding normal tissues below damaging thresholds as much as possible.


Radiation therapy is used as a primary, curative treatment, as a palliative treatment, and/or as adjunctive therapy. It can be used pre-operatively or post-operatively, and in combination with chemotherapy, biologic agents, and hormonal agents. The radiation dose prescribed to achieve tumour control is often limited by the radiosensitivity of normal tissues, which are located around the tumour, and thus may result in early and late adverse side effects. Some adverse effects are unavoidable and often resolve spontaneously or with treatment. Serious adverse effects may occur and result from the proximity of sensitive normal tissues to the treatment area. However, such adverse side effects do not undermine the purpose of radiation therapy. Appropriate use of radiation therapy saves millions of lives every year. Even if only palliative treatment is possible, the therapy reduces suffering substantially. There are also a few non-malignant diseases whose treatment by radiation is a method of choice. Note that palliative radiotherapy and radiotherapy of non-malignant diseases uses much lower doses, generally not inducing any acute side effects.


Radiation therapy has benefited greatly from technological advances over the past two decades, resulting in a wide variety of available delivery methods: Intensity-modulated radiation therapy (IMRT) utilizing techniques to quantify the critical normal tissue doses; Image-guided radiotherapy (IGRT) utilizing real-time imaging for treatment localization during radiotherapy; Stereotactic radiosurgery (SRS) delivering of a large dose per fraction to treat focal brain lesions and its extension, stereotactic body radiation therapy (SBRT), to treat focal lesions in the lung, spine, liver, pancreas, prostate and all parts of the body; Particle beam radiotherapy utilizing protons, neutrons or other heavy particles; Brachytherapy placing sealed radioactive sources near the tumor; Intraoperative radiotherapy (IORT) delivering to the surgical bed after removal of the tumor or to the tumor itself at the time of surgery; Unsealed sources delivering a radiopharmaceutical orally or parenterally; and Hyperthermia adding of heat to radiotherapy.


The advance of technology inevitably results in an increase in complexity and opportunities for new types of human error and equipment problems. Ongoing education and training of members of the radiotherapy team with respect to new and evolving technologies is crucial, as is adherence to clearly defined quality assurance policies and procedures.

  • ICRP Publication 112 Preventing Accidental Exposures from New External Beam Radiation Therapy Technologies provides recommendation and guidance on preventing accidental exposures from new external beam radiation therapy technologies
  • ICRP Publication 97 Prevention of High-dose-rate Brachytherapy Accidents and ICRP Publication 98 Radiation Safety Aspects of Brachytherapy for Prostate Cancer using Permanently Implanted Sources discuss safety aspects of brachytherapy
  • ICRP Publication 127 Radiological Protection in Ion Beam Radiotherap addresses protection in ion beam radiotherapy
  • ICRP Publication 86 Prevention of Accidents to Patients Undergoing Radiation Therapy covers prevention of accidental exposures to patients undergoing radiation therapy


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Yoon, H., Shah, K., Small, W. Jr., Mehta, M., Hayes, J., Chapter 1: Basic Concepts of Clinical Radiation Oncology. In: Clinical Radiation Oncology, 3e. Small, W. Jr., (ed): John Wiley & Sons, 2017, pp. 3-14.