An Analysis of Treatment Failure in Wilms Tumor (WT): A Report from the Central American Association of Pediatric Hematology/Oncology (AHOPCA)

57 Background: Patients with WT in AHOPCA present late with large abdominal masses, in poor clinical condition. This analysis focuses on treatment failure.Methods: Between 2012 and 2015, 182 evaluable patients were diagnosed with unilateral WT. Patients were staged with abdominal ultrasound/computed tomography and thorax radiograph/CT. Therapy was adapted from National Wilms Tumor Study-5 except for patients with large abdominal masses and/or severe malnutrition who received preoperative doxorubicin, vincristine, actinomycin-D for 4 to 6 weeks. Treatment failure was defined as abandonment of therapy, recurrent/progressive disease (PD), and death: early ( 2 weeks after diagnosis).Results: 49% were male; 23% were <2 years (median age 3.5y). Stage distribution: I, 8; II, 21; III, 116; IV, 37 cases. For 123/181 (68%) preoperative therapy was warranted (volume 579cm 3 ). Treatment failures were: recurrence/PD 28; abandonment 19; early death 3, and toxic death 2. 2/29 (7%) patients with stage I/II suffered recurrence/PD, 13/116 (11%) stage III, and 13/37 (35%) stage IV. Most failures were metastatic (68%). Abandonment-sensitive 3-years EFS was 68%±0.04% (SE) for the all stages, 77%±0.043% abandonment-censored, and abandonment-sensitive OS was 71%±0.05%.Conclusion: Multicenter protocol-driven therapy tailored to fit regional needs is feasible in patients with WT. Abandonment remains a challenge as do early and toxic deaths due to advanced disease presentations in fragile children. Compared to previous eras 2000-2004 (3-year EFS 50%±4.3% and 2005-2011 (3-year EFS 59%±3.1%) survivals continue to improve. This improvement reflects the engagement of the whole multidisciplinary team including surgery, radiation oncology, and pathology.AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST: No COIs from the authors.