Results of the United Kingdom Children's Cancer Study Group first Wilms' Tumor Study.

Purpose: The first United Kingdom Children's Cancer Study Group (UKCCSG) Wilms' Tumor Trial (UKW1) applied treatment regimens stratified by stage and histology in accordance with National Wilms' Tumor Study (NWTS) criteria, seeking to reduce treatment of low-stage, favorable-histology (FH) tumors without impairing survival and to improve prognosis of stage III and IV (FH) and unfavorable-histology (UH) tumors with more intensive chemotherapy.

Patients And Methods: Three hundred eighty-four consecutively diagnosed patients with Wilms' tumor were recruited from the 20 UKCCSG centers and Oslo, Norway, between January 1980 and June 1986. The regimen for stage I patients was vincristine (Vcr) only, while stage II patients received Vcr and dactinomycin (Act-D). Stage III patients received three-drug therapy and stage IV and UH patients four-drug regimens. Act-D was given as pulsed doses of 1.5 mg/m2 every 3 or every 6 weeks. No lung irradiation was used in stage IV patients. No randomized comparisons were attempted. End points were survival and event-free survival (EFS).

Results: Survival at 6 years in FH patients was 96% for stage I, 93% for stage II, 83% for stage III, 65% for stage IV, and 50% for UH patients of all stages.

Conclusion: Vcr alone is as effective for stage I FH tumors as the two-drug regimen used in the NWTS and International Society of Pediatric Oncology (SIOP) studies. Fractionation of Act-D is unnecessary. The poorer results for stage IV FH and UH patients compared with the NWTS may be due to treatment differences, such as the use of lung irradiation for stage IV FH patients in NWTS3, and/or to case selection bias.