[Which constraints for which organs at risk in radiotherapy for adult patients?]

The delineation of organs at risk is a part of the planning of irradiation treatments. With the delineation of the target volumes, this task is essential and is followed by the appropriate calculations of a dose distribution from radiation beams and the validation of the treatment plan. The contouring of organs at risk could influence the dosimetric parameters, treatment planning and also the outcome of the patient. The treatment intent (curative or palliative), doses and fractionations and also the type of organs at risk have an impact on the delineation. Optimized radiation techniques and reirradiations make delineation and definition of doses constraints more difficult. The second edition of the guidelines established by the French society of radiation oncologists (SFRO) includes a chapter dedicated to the delineation of organs at risk and dose constraints. The transposition of these recommendations in current practice remains the responsibility of the radiation oncologist who implements them and who has to judge their relevance.