The Vertebrae as OARs in Paediatric Radiotherapy Clinical Trials: Initial QUARTET experience.

Irradiation of the vertebrae in prepubertal patients can result in growth defects and deformities, related to inhomogeneities in dose distribution. In 2019 the SIOPE-ROWG published a consensus on vertebral delineation and constraints in an effort to standardise practice across Europe. QUARTET is a SIOPe project for RTQA in Paediatric Clinical Trials across Europe. All trials incorporate specific guidelines which include recommendations on vertebral delineation and dosimetry as per the 2019 ROWG consensus. We performed an audit of the first cases enrolled in the trials using QUARTET for RTQA, aiming to identify the main protocol deviations in vertebral delineation and their impact on dosimetry. All cases undergoing QUARTET review until 22/02/2022 were evaluated. Pre-pubertal patients with vertebrae in the proximity of the target volume were included. Vertebrae adjacent to the target volume (VBs_Adj) and directly cranial and caudal (VB_NAdj_S/I) were assessed for compliance to delineation and dosimetry guidelines by a second, independent reviewer. Missing or non-compliant structures were recontoured and the new DVH metrics were compared with the initial ones. 51 patients were included. VB_NAdj_S/I were not delineated in 49% of the cases. Dose constraints for VBs _Adj were met in 31% of initial submissions. Dosimetry compliance for VB_NAdj_S/I was 53% for photons and 16% for protons. Resubmission for vertebral delineation or dose issues was required for 20% of cases. Approximatively 70% of VBs delineations include spinal processes and spinal canal. When re-delineated, only 14% of the VBs_Adj met the dosimetry constraints. Despite the availability of international consensus guidelines, a high variability in vertebrae delineation is observed in QUARTET cases, with impact on dosimetry. Better vertebral sparing was observed in photon cases. Guidelines will be amended to reflect these results and further improve compliance. [ABSTRACT FROM AUTHOR]