Session

Overview: The definition of safety margins around the CTV an essential step in radiotherapy. Depending on the treatment methods, the definition of these margins is based on good practice rules or formulas ensuring a given dosimetric coverage of the CTV for a certain number of patients. These margins have historically been defined for external radiotherapy with high-energy X-rays. During this symposium, we will re-explore the relevance of these safety margins for treatment methods that differ more or less strongly from the conditions for which the margins were defined/calculated at the start. What about the relevance of margins for online adaptive radiotherapy with MRI? Can we greatly reduce them, thanks to the information gleaned from imagery? For proton therapy, the weakness of margining models is well documented. How to compensate it? Finally, brachytherapy also requires a specific approach to secure target coverage, since the possibilities to steer dose gradients are substantially different from in EBRT