AA, abdominal aorta; AP/PA, Anterior-Posterior/Posterior-Anterior; CT, Computed Tomography; CTV-N, Clinical Target Volume of the lymph node area; CTV-T, Clinical Target Volume of the primary Tumor; DICOM, Digital Imaging and Communications in Medicine; DSC, Dice Similarity Coefficient; Flank target volume; GTVpre/post, pre- and postoperative Gross Tumor Volume respectively; HR, High-Risk; Highly-conformal radiotherapy; IGRT, Image-Guided Radiotherapy; IMRT, Intensity-Modulated Radiotherapy; IR, Intermediate-Risk; IVC, inferior vena cava; Inter-clinician variation; MRI, Magnetic Resonance Imaging; OAR, organs at risk; Pediatric renal tumors; Quality assurance; RT, radiotherapy; RTOG, Radiation Oncology Group; RTSG, Renal Tumor Study Group; SIOP, International Society for Pediatric Oncology; TVintersect, intersect target volume; TVref, reference target volumes; WT, Wilms' tumor; Wilms tumor; n.a., not applicable; part, participant; ref, reference