Updated favourable-histology Wilms tumour risk stratification: rationale for future Children's Oncology Group clinical trials.

Patients with Wilms tumour have benefited from the results of decades of large collaborative clinical trials, leading to improved care. In the National Wilms Tumor Study Group and now Children's Oncology Group (COG) trials, risk stratification evolved and expanded with each generation of studies and, therefore, ensuring that each patient receives the appropriate therapy has become increasingly complex. A new risk stratification system has been developed that forms the basis of the upcoming COG favourable-histology Wilms tumour (FHWT) study. Topics of diagnostic and prognostic uncertainty, such as the findings of tumour pulmonary emboli or extra-abdominal lymphadenopathy at diagnosis, will be integrated into the central review determination of staging of FHWT by committee consensus to facilitate clinical classification for therapeutic studies. Clear documentation of the elements of current risk stratification are of particular importance as refinement of the classification of patients with FHWT continues in an effort to optimize research, personalize treatment and provide an educational resource.