Kidney tumors are the second most common non-CNS tumors in children. Wilms tumors (WT) are the most frequent tumor type, but also non-Wilms tumors occur, i.e. clear cell sarcoma of the kidney (CCSK), renal cell carcinoma (RCC), congenital mesoblastic nephroma (CMN) and malignant rhabdoid tumors of the kidney (MRTK). Treatment of children with kidney tumors starts with chemotherapy, without histological confirmation and is followed by surgery. This avoids tumor rupture and subsequent radiotherapy, with its attendant late effects in these young children. However, non-WT often needs more intensive treatment. Hence radiological innovation to discriminate tumor types is of utmost importance. In the new SIOP Umbrella protocol for pediatric renal tumors, MRI is introduced for diagnosis, evaluation of treatment response and follow-up. Over the last decade radiological progress has been made by introduction of Diffusion Weighted Imaging (DWI). Preliminary studies have suggested that characterization of renal tumor types is feasible, and that nephroblastoma subtypes (blastemal, stromal, epithelial) may be discriminated, but several key questions remain unanswered, as validation studies with substantial numbers are lacking.
The ultimate aim of this study is a personalized MRI diagnosis and treatment response assessment in children with kidney tumors which will impact early treatment decisions that can either lead to enhanced survival as well as reduced treatment related toxicity.