text: Historically, the three main divisions of radiation therapy are:
  * external beam radiation therapy (EBRT or XRT) or teletherapy;
  * brachytherapy or sealed source radiation therapy; and
  * systemic radioisotope therapy or unsealed source radiotherapy.
  The differences relate to the position of the radiation source; external is outside the body, brachytherapy uses sealed radioactive sources placed precisely in the area under treatment, and systemic radioisotopes are given by infusion or oral ingestion. Brachytherapy can use temporary or permanent placement of radioactive sources. The temporary sources are usually placed by a technique called afterloading. In afterloading a hollow tube or applicator is placed surgically in the organ to be treated, and the sources are loaded into the applicator after the applicator is implanted. This minimizes radiation exposure to health care personnel.
  Particle therapy is a special case of external beam radiation therapy where the particles are protons or heavier ions.
  A review of radiation therapy randomised clinical trials from 2018 to 2021 found many practice-changing data and new concepts that emerge from RCTs, identifying techniques that improve the therapeutic ratio, techniques that lead to more tailored treatments, stressing the importance of patient satisfaction, and identifying areas that require further study.