A Baseline Survey on the Treatment Workflow and Pediatric IGRT Practice Among European Members of the Project-Based Consortium and the Pediatric Radiation Oncology Society (PROS).

Background Image-guided radiotherapy (IGRT) enables high precision tumor treatment with potential for sparing healthy tissues. The value of pediatric IGRT is widely acknowledged, but there is no consensus on ‘best practice’. We aimed to assess clinical pediatric IGRT practice among European members of the Pediatric Radiation Oncology Society (PROS) and members of our project-based consortium.Methods A survey addressing radiotherapy preparation, planning and delivery in seven treatment sites was sent to European PROS members and/or our IGRT project-based consortium (70 institutes). Responses were collected from June-September 2018.Results Of the 42 responding institutes (response rate 60%), 33 indicated to treat children. 28/33 are photon-only institutes, 3/33 are dedicated proton (‘proton-only’) institutes and 2/33 use both. Immobilization includes facial masks (in 100% of brain, craniospinal axis (CSA) and head-and-neck (H&N) treatments), and vacuum cushions (all sites, except brain and H&N). Intensity-modulated radiotherapy and volumetric-modulated arc therapy are most frequently applied ranging from 71%-81% in respectively CSA (20/28), and extremities (21/26), followed by 3D conformal radiotherapy ranging from 36%-69% in respectively H&N (10/28), and extremities (18/26). Isotropic planning target volume (PTV) margins varied widely in brain and abdomen (range, 1-10mm). The use of in-room kilovolt cone-beam computed tomography ranges from 57%-86% in respectively CSA (16/28), and thorax (24/28). Daily online imaging is used by the majority of institutes, ranging from 85%-90% in respectively extremities (22/26) and pelvis (27/30). Offline imaging protocols are used by 14%-21% in respectively H&N (4/28) and thorax (6/28).Conclusions Our survey shows comparable practice in pre-treatment imaging, planning and treatment techniques, and IGRT application among the participating European institutes. However, wide ranges in PTV margin sizes exist, supporting the need to define international ‘best practice’ guidelines for pediatric IGRT, and to aim for consensus on optimal margin definitions in view of available IGRT facilities and workflows among institutes.