Epidemiological features of Wilms' tumor: results of studies by the International Society of Paediatric Oncology (SIOP).

This descriptive epidemiology study of 1,040 children with Wilms' tumor (WT) registered in the International Society of Paediatric Oncology (SIOP) clinical trials confirms the findings reported by the National Wilms' Tumor Study. The male:female rate was 0.89:1. The mean age at diagnosis of the 43 bilateral cases was significantly younger than children with unilateral renal involvement (32.4 vs 45 months). However, the mean ages of diagnosis for unilateral multicentric and for unicentric WT were very similar. On the other hand, the mean age at diagnosis of children with sporadic aniridia and hypospadias was younger than the mean age of patients with or without other congenital malformations. Thus aniridia as well as hypospadias could be indices of the first mutation, according to the Knudson and Stron hypothesis. WT was reported in two members of each of five families. However, these familial cases were comparable in terms of demographic and clinical features to the nonfamilial ones. These data suggest that the heritable fraction of WT is relatively small and that genetic and environmental factors interact in the development of WT.