Influence of radiation therapy delay on abdominal tumor recurrence in patients with favorable histology Wilms' tumor treated on NWTS-3 and NWTS-4: a report from the National Wilms' Tumor Study Group.

Purpose: This study was undertaken to determine whether radiation therapy (RT) delay of >or=10 days had an adverse impact on abdominal tumor recurrence among children with favorable histology (FH) Wilms' tumor enrolled in National Wilms' Tumor Study (NWTS) 3 and 4.

Methods And Materials: A total of 1226 patients with Stage II-IV FH tumors who received flank or abdominal RT in NWTS-3 and NWTS-4 were included in this analysis. Recurrent disease in the operative bed was classified as flank recurrence.