Since 2000, centers across Central America have shared treatment guidelines for Wilms tumor, using histology (anaplasia present or absent) and tumor stage to stratify patients into low-, intermediate-, and high-risk groups. Weekly virtual tumor board meetings involving local and international experts were held to ensure consistent treatment assignments. We analyzed data from 367 children with unilateral tumors treated per these guidelines. Five-year abandonment-sensitive event-free and overall survival estimates were: low risk 82% ± 3.8% and 86% ± 3.6%, intermediate risk 50% ± 3.4% and 60% ± 3.4%, and high risk 36% ± 7.6% and 45% ± 7.9%. Survival outcomes were suboptimal, primarily due to advanced disease in fragile children at presentation and abandonment of treatment.