Adaptive radiotherapy in paediatric patients: a SIOP Europe ROWG survey on practice patterns across Europe

Objectives: Adaptive radiotherapy (ART) is increasingly recognized for its potential to optimize treatment accuracy by adjusting to anatomical changes during therapy. In children, who are particularly sensitive to radiation-induced toxicities and experience rapid anatomical changes, ART could be especially beneficial. We conducted an online survey to assess the current state of ART in children across Europe. Methods: A 21-question survey regarding ART implementation, techniques, indications, and technical infrastructure was distributed online to SIOP-Europe affiliated centres. Results: Sixty responses from 18 European countries were received. ART was available for children in 68% of centres. Most frequent sites for implementation were pelvis, abdomen, and head-and-neck, with an average of 20% of respondents using ART for >75% of these cases. Higher-volume centres were more likely to implement ART (r = 0.34, P = .048). Fifteen percent performed daily adaptation, while 75% applied it only for major anatomical changes. Half of the centres used offline and 24% online ART. Specific infrastructure included Ethos (21%), MR-LINAC (5%), and Tomotherapy (13%). Automatic contouring was mostly used for OARs (57%). Barriers to implementation included a need for more evidence (50%), specialized equipment (52%) and guidelines (39%). Conclusions: ART use in paediatric patients is highly variable and remains limited. Only a subset of centres reported routine use of ART, with notable variation in frequency and criteria for adaptation. Advances in knowledge: This is the first Europe-wide survey to comprehensively map ART practices in paediatric oncology, revealing substantial heterogeneity and identifying key barriers to wider adoption, representing a base to guide standardization and future clinical validation.