Treatment of children with favorable histology Wilms tumor with extrapulmonary metastases: A report from the COG studies AREN0533 and AREN03B2 and NWTSG study NWTS‐5

Background Patients with stage IV favorable histology Wilms tumor (FHWT) with extrapulmonary metastases (EPM) constitute a small subset of patients with FHWT. Because of their rarity and heterogeneity, optimal FHWT treatment is not well understood. Children’s Oncology Group protocol AREN0533 assigned patients with FHWT and EPM to intensified chemotherapy, regimen M, after initial DD‐4A chemotherapy. To improve understanding of prognostic factors and best therapies, experiences of patients with EPM on AREN0533, as well as on protocols AREN03B2 and NWTS‐5, were reviewed. Methods Combined outcomes for patients with EPM from NWTS‐5, AREN0533, and AREN03B2 were determined. Those treated on AREN0533 were compared with those treated on NWTS‐5. Prognostic factors were explored in the pooled cohort. Results Forty‐seven patients with FHWT with EPM enrolled on AREN0533, 37 enrolled on NWTS‐5, and 64 were followed only on AREN03B2. The pooled cohort of all 148 patients demonstrated a 4‐year event‐free survival (EFS) of 77.3% (95% CI, 70.8–84.4) and 4‐year overall survival of 88.9% (95% CI, 83.9–94.2). Four‐year EFS of patients with EPM treated on AREN0533 was 76.0% (95% CI, 64.6–89.4) vs 64.9% (95% CI, 51.7–82.2) on NWTS‐5; hazard ratio, 0.64, p = .26; no difference in overall survival was observed. Increasing linear age and slow incomplete lung response were associated with worse EFS in a pooled cohort. Conclusions Outcomes for patients with EPM are among the lowest for children with FHWT. Further trials with standardized surgical and radiation treatment to metastatic sites, and prospectively collected biologic and treatment details are needed. Clinical trial registration Clinical Trials.gov identifiers: NCT00379340, NCT00898365, and NCT00002611. Pooled outcomes across three studies of patients with favorable histology Wilms tumor and extrapulmonary metastases revealed 4‐year event‐free survival of 77.3% and overall survival of 88.9%, with no statistical differences seen between patients on AREN0533 compared with those on NWTS‐5. Missing details on local management of metastatic sites informs a critical need for better data capture in future studies to optimize local control strategies and chemotherapy regimens for this higher‐risk favorable histology Wilms tumor patient group.