<prompt> Which of the following is post-chemotherapy based staging system in Wilms tumor?National Wilms tumor staging system NWTSInternational society of pediatric oncology ISPOAJCCTNMChadwick  <response>: a. National Wilms tumor staging system NWTSRef: Nelsons 20e p 2464-2466, Ghai 8e 617-618The two major groups which have tremendous contributions in the management of Wilms tumor are National Wilms Tumor Study NWTS and the Societe Internationale Doncologie Pediatrique SIOP.In 2001, NWTS merged with several other pediatric oncology cooperative groups to create the Childrens Oncology Group COG. However, the NWTS is still active in name today completing follow-up of the late effects of treatment for patients previously enrolled in its trials. 