Impact of Pulmonary Tumor Burden in Favorable Histology Wilms Tumor Outcomes: A Report From the Children's Oncology Group Study AREN0533

PURPOSE Children with favorable histology Wilms tumor (FHWT) with pulmonary metastases have inferior outcomes compared with those with localized disease. We evaluated the impact of pulmonary tumor burden within subgroups of similarly treated children with stage IV FHWT. METHODS Children with FHWT with pulmonary-only metastasis enrolled in AREN0533 were included. Lung nodule response assessment, by chest computed tomography after two cycles of vincristine/dactinomycin/doxorubicin (Regimen DD-4A) chemotherapy, identified rapid complete responses (RCRs) and slow incomplete pulmonary nodule responses (SIRs). Event-free survival (EFS) and overall survival (OS) were compared by number and size of pulmonary metastases within two cohorts: (1) RCR treated with additional DD-4A without lung radiation therapy (RT) and (2) SIR treated with the original three drugs plus cyclophosphamide/etoposide (Regimen M) with lung RT. The multivariable Cox proportional hazards model for EFS and OS stratified by treatment assessed the impact of the number and size of pulmonary metastases adjusted for tumor 1q gain. RESULTS AREN0533 enrolled 288 children with stage IV pulmonary-only metastases, of whom 251 met inclusion criteria for outcome analyses. In the RCR cohort (n = 105), EFS and OS were not significantly different based on the number of lung metastases, whereas size of pulmonary metastases was significantly associated with EFS ( P = .022), but not OS. In the SIR cohort (n = 146), EFS and OS did not differ by the number or size of lung metastases. In multivariable models, neither number nor size of lung metastases was significantly associated with EFS or OS although 1q gain was significant (EFS P = .0015; OS P = .039) after adjustment for these factors. CONCLUSION 1q gain is a superior prognostic indicator to pulmonary tumor burden in patients with FHWT with pulmonary-only metastasis.