A Study Using Risk Factors to Determine Treatment for Children With Favorable Histology Wilms Tumors (FHWT)

Inclusion Criteria: * Patients must be enrolled on APEC14B1 and consent to Part A - Eligibility Screening prior to enrollment on AREN2231. * Patients must be \< 30 years old at enrollment. * Patients with newly diagnosed Stage I-IV Favorable Histology Wilms Tumor confirmed by central review and with a qualifying Initial Stratum Assignment on APEC14B1. * Patients must receive a qualifying Initial Stratum Assignment on APEC14B1-REN by Day 14 post-diagnostic procedure (nephrectomy or biopsy), where that procedure is Day 0. * Patients must enroll on AREN2231 by Day 14. * Exceptions: If patient reaches Day 14 (post initial diagnostic nephrectomy or biopsy) without receiving an Initial Stratum Assignment on APEC14B1-REN, patient will not be eligible for enrollment on AREN2231 unless all required materials (reports and Case Report Forms and specimens) for an Initial Stratum Assignment arrived by Day 7, but an Initial Stratum Assignment was not completed by Day 14. In these circumstances, after obtaining appropriate protocol consent, the patient may proceed with treatment according to local institutional staging and enroll within 5 calendar days of notification of the central Initial Stratum Assignment being issued, only if the AREN2231 Initial Stratum Assignment is in agreement with any treatment already initiated. If the Initial Stratum Assignment is not in agreement with the local institution's assessment then the patient will be ineligible for AREN2231. * All sites must hav…