Organs at Risk Radiation Dose Constraints: 2025 Update

We present the updated recommendations from the Société française de radiothérapie oncologique (SFRO, the French society for radiation oncology) regarding radiation dose constraints for organs at risk in adult patients, with the aim of supporting clinical decision-making in contemporary radiotherapy practice. These guidelines address a wide range of clinical scenarios, including normofractionation, hypofractionation, stereotactic radiotherapy, and reirradiation. Dose constraints are essential to ensure both the safety and efficacy of radiotherapy, especially with the growing use of advanced techniques such as intensity-modulated radiotherapy and stereotactic body radiotherapy. However, given the wide range of existing dose constraints and the lack of harmonization across different practices, this work aims to provide a unified and updated framework adapted to modern radiotherapy techniques. Moreover, many of these constraints are still based on data derived from three-dimensional conformal radiotherapy, which necessitates cautious application when extrapolated to more advanced techniques. Clinical judgment remains crucial, particularly in complex cases such as re-irradiation or treatments using altered fractionation schedules. These updated consensus aim to provide a practical and evidence-based framework to help radiation oncologists and medical physicists minimize the risk of toxicity to normal tissues. By consolidating and adapting current knowledge to modern radiotherapy techniques, they serve as a useful tool in daily clinical practice.