The Third National Wilms' Tumor Study sought to reduce treatment for low-risk patients and find better chemotherapy for those at high risk for relapse. Eligible patients (1439) were randomized according to stage (I-IV) and histology (favorable [FH] or unfavorable [UH]), and contributed data to survival and relapse-free survival (RFS) analyses. Four-year (postnephrectomy) survival percentages and randomized treatment regimens for low-risk patients were 96.5% for 607 Stage I/FH patients who received dactinomycin (Actinomycin D [AMD], Merck Sharp & Dohme, West Point, PA) and vincristine (VCR) for 10 weeks versus 6 months; 92.2% for 278 Stage II/FH patients; and 86.9% for 275 Stage III/FH patients who received AMD + VCR +/- Adriamycin (ADR, Adria Laboratories, Columbus, OH) for 15 months. Stage II/FH patients also had either zero or 2000 cGy irradiation (RT) postoperatively and Stage III/FH patients either 1000 or 2000 cGy. Four-year survival was 73.0% for 279 high-risk patients (any Stage IV, all UH) who received postoperative radiation therapy (RT) and AMD + VCR + ADR +/- cyclophosphamide (CPM). Statistical analysis of survival and RFS experience shows that the less intensive therapy does not worsen results for low-risk patients and CPM does not benefit those at high risk.

An analysis of information on 2,961 patients with Wilms tumor entered in the National Wilms Tumor Study up to July 1983 revealed 13 tumors occurring in horseshoe kidneys. The correct preoperative diagnosis was made in 6 of the 13 patients. At presentation 5 patients had stage 1, 3 stage 2 and 5 stage 3 disease. Major preoperative or intraoperative tumor spillage occurred in 3 patients. The over-all survival rate was 85 per cent after a mean followup of 45 months. The surgical, pathological and therapeutic aspects of Wilms tumor in horseshoe kidneys were analyzed carefully. The frequency of horseshoe kidneys in patients with Wilms tumor registered with the National Wilms Tumor Study was determined and was used in conjunction with population data to estimate the relative risk of Wilms tumor occurrence in children with horseshoe kidneys.