Treatment of stage I anaplastic Wilms' tumour: a report from the Children's Oncology Group AREN0321 study

Background: In the fifth National Wilms Tumor Study (NWTS-5), the 4-year event-free survival (EFS) and overall survival (OS) estimates for 29 patients with stage I focal (n = 10) or diffuse (n = 19) anaplastic Wilms' tumour (AWT) treated with vincristine and dactinomycin without flank radiation were 69.5% and 82.6%, respectively. The Children's Oncology Group AREN0321 study evaluated whether adding doxorubicin and flank radiation improves survival for these patients. Patients and methods: Tumour histology and stage were confirmed by real-time central pathology, surgery and radiology review. The patients received 25 weeks of vincristine, dactinomycin and doxorubicin (cumulative dose 150 mg/m²) with flank radiation (1080 cGy). We retrospectively analysed outcomes of all patients with stage I AWT enrolled in NWTSs 1–5 and AREN0321 with respect to treatment regimens. Results: Eighteen patients with stage I AWT (8 focal and 10 diffuse) were enrolled on AREN0321. With a median follow-up of 4.6 years, the 4-year EFS and OS were 100%. One patient with diffuse AWT had pulmonary relapse 4.12 years after diagnosis. In the 112 patients with stage I AWT treated in NWTSs 1–5 and AREN0321, the EFS was significantly improved with doxorubicin treatment (p = 0.01; 4-year EFS: 97.2% [95% confidence interval {CI}: 91.3–100] vs. 77.5% [95% CI: 67.6–87.4]) but not by flank radiation (p = 0.15). Conclusions: Treatment of stage I AWT with vincristine, dactinomycin, doxorubicin and flank radiation in AREN0321 yielded excellent survival outcomes. Retrospective analysis of AREN0321 and NWTS patients suggests that doxorubicin had a greater contribution to the excellent outcomes than radiation.