1.1 Primary Aims 1.1.1 Stage I Nephrectomy Only Stratum 2. To maintain EFS for Stage I FHWT patients without adverse biology who are also (1) 2 to < 4 years of age, OR (2) age < 2 years with tumor weight of 550 grams or more, OR (3) age 4+ years with epithelial histology subtype while reducing post-nephrectomy therapy from EE 4A to Nephrectomy Only. 1.1.2 Stage I EE-4A Stratum 3. To improve EFS for Stage I FHWT patients with age < 2 years AND nephrectomy weight < 550g AND whose tumors have adverse biology by treating with EE-4A instead of Nephrectomy Only. 1.1.3 Stage II: VIVA vs DD-4A Randomization. To evaluate whether addition of vincristine and irinotecan to standard EE-4A (novel Regimen VIVA) is non inferior to DD-4A in terms of EFS among Stage II FHWT patients whose tumors demonstrate adverse biology. 1.1.4 Stage III: EE-4A. To evaluate whether omission of doxorubicin (EE-4A) is non inferior to historical DD-4A in Stage III FHWT patients without adverse biology or post-therapy blastemal predominance. 1.1.5 Stage III: Regimen MVI vs Regimen M Randomization. To demonstrate the non-inferiority of Regimen MVI to Regimen M in the treatment of Stage III FHWT patients whose tumors exhibit adverse biology (post-chemotherapy blastemal predominance excluded). 1.1.6 Stage IV: Regimen MVI vs Regimen M Randomization. To demonstrate the non-inferiority of Regimen MVI to Regimen M in the treatment of Stage IV FHWT patients with adverse biology, slow incomplete lung response (SIR), or extrapulmonary metastases (EPM) (post-therapy blastemal predominance excluded). 1.1.7 Stage III-IV: UH-3 (Blastemal Predominance). To demonstrate the superiority of Regimen UH-3 vs historical DD-4A or Regimen M in treatment of Stage III or IV FHWT patients with blastemal predominance at delayed nephrectomy. 1.2 Secondary Aims - Please see protocol