BACKGROUND: The SIOP-Renal Tumor Study Group (RTSG) does not advocate invasive procedures to determine histology before the start of therapy. This may induce misdiagnosis-based treatment initiation, but only for a relatively small percentage of approximately 10% of non-Wilms tumors (non-WTs). MRI could be useful for reducing misdiagnosis, but there is no global consensus on differentiating characteristics. PURPOSE: To identify MRI characteristics that may be used for discrimination of newly diagnosed pediatric renal tumors. STUDY TYPE: Consensus process using a Delphi method. POPULATION: Not applicable. FIELD STRENGTH/SEQUENCE: Abdominal MRI including T1- and T2-weighted imaging, contrast-enhanced MRI, and diffusion-weighted imaging at 1.5 or 3 T. ASSESSMENT: Twenty-three radiologists from the SIOP-RTSG radiology panel with ≥5 years of experience in MRI of pediatric renal tumors and/or who had assessed ≥50 MRI scans of pediatric renal tumors in the past 5 years identified potentially discriminatory characteristics in the first questionnaire. These characteristics were scored in the subsequent second round, consisting of 5-point Likert scales, ranking- and multiple choice questions. STATISTICAL TESTS: The cut-off value for consensus and agreement among the majority was ≥75% and ≥60%, respectively, with a median of ≥4 on the Likert scale. RESULTS: Consensus on specific characteristics mainly concerned the discrimination between WTs and non-WTs, and WTs and nephrogenic rest(s) (NR)/nephroblastomatosis. The presence of bilateral lesions (75.0%) and NR/nephroblastomatosis (65.0%) were MRI characteristics indicated as specific for the diagnosis of a WT, and 91.3% of the participants agreed that MRI is useful to distinguish NR/nephroblastomatosis from WT. Furthermore, all participants agreed that age influenced their prediction in the discrimination of pediatric renal tumors. DATA CONCLUSION: Although the discrimination of pediatric renal tumors based on MRI remains challenging, this study identified some specific characteristics for tumor subtypes, based on the shared opinion of experts. These results may guide future validation studies and innovative efforts. LEVEL OF EVIDENCE: 3 Technical Efficacy Stage: 3.

Center for Medical Imaging and Physiology Skåne University Hospital Lund University Lund Sweden

Clinic of Diagnostic and Interventional Radiology Division of Pediatric Radiology Heidelberg University Hospital Heidelberg Germany

Department of Diagnostic Imaging Escola Paulista de Medicina UNIFESP São Paulo Brazil

Department of Paediatric Radiology Great Ormond Street Hospital NHS Foundation Trust London UK

Department of Paediatric Radiology Institute for Maternal and Child Health IRCCS Burlo Garofolo Trieste Italy

Department of Paediatric Radiology Leeds Teaching Hospitals Leeds UK

Department of Pathology University Medical Center Utrecht Utrecht The Netherlands

Department of Pediatric Imaging Hôpital d'Enfants Armand Trousseau APHP Paris France

Department of Pediatric Oncology and Hematology Saarland University Medical Center and Saarland University Faculty of Medicine Homburg Germany

Department of Pediatric Radiology and Nuclear Medicine 'Aghia Sophia' Children's Hospital Athens Greece

Department of Pediatric Radiology Hospital Vall d'Hebron Barcelona Spain

Department of Pediatrics Semmelweis University Budapest Hungary

Department of Radiology 2nd Faculty of Medicine Charles University and University Hospital Motol Prague Czech Republic

Department of Radiology and Nuclear Medicine University Medical Center Utrecht Wilhelmina Children's Hospital Utrecht University Utrecht The Netherlands

Department of Radiology Bambino Gesù Children's Hospital Rome Italy

Department of Radiology Fondazione IRCCS Istituto Nazionale dei Tumori Milan Italy

Department of Radiology St Anna Children's Hospital University Clinic of Pediatrics Medical University of Vienna Vienna Austria

Department of Radiology University Hospitals Leuven Leuven Belgium

Division of Pediatric Radiology Department of Radiology University Hospital Tübingen Tübingen Germany

Imaging Department Institut Curie Paris France

Institute of Diagnostic and Interventional Radiology University Hospital Zurich Zurich Switzerland

Princess Máxima Center for Pediatric Oncology Utrecht The Netherlands

Radiology Unit Fondazione IRCCS Istituto Nazionale dei Tumori Milan Italy

Section of Pediatric Radiology Institute of Diagnostic and Interventional Radiology University Hospital Jena Jena Germany

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White paper on the current state of imaging biomarkers in paediatric oncology