Results of the Latin American Pediatric Oncology Group (GALOP) Trial for Patients With Metastatic Ewing Sarcoma: Multicentric study of Interval‐Compressed Multiagent and Metronomic Chemotherapy

ABSTRACT Background GALOP investigators developed a multicenter protocol to standardize treatment for newly diagnosed metastatic Ewing sarcoma (ES) in South America. Methods Prospective trial. Induction chemotherapy consisted of 9 alternating interval‐compressed cycles (every 14 days) of vincristine, doxorubicin, cyclophosphamide, and ifosfamide–etoposide; local and metastatic site control; and 5 consolidation cycles (every 21 days), followed by MCT with cyclophosphamide and vinblastine for 1 year. Results Between 2011 and 2019, 198 patients were recruited from 34 centers in Argentina, Brazil, Chile, and Uruguay. Characteristics include: male patients (60.6%), median age of 12.3 years (range, 0.8–31.1); axial primary localization (62.1%), size >8 cm (70.2%); and bone origin (71.2%). Metastatic sites were lung, extra‐lung, and combined in 43.4%, 31.3%, and 25.3%, respectively. The overall response rate was 79.3%, and local treatment was performed in 85.3% of patients. With a median follow‐up of 65.1 months (95% CI: 53.9–76.4), the 5‐year overall survival (OS) and event‐free survival (EFS) were 33.1% (95% CI: 25.9–40.4) and 27.8% (95% CI: 21.5–34.3), respectively. The 5‐year OS was 44.9%, 31.3%, and 15.6% for lung, extra‐lung, and combined, respectively ( p < 0.001). The median interval between induction chemotherapy cycles was 17 days, with a febrile neutropenia rate of 19.3%. Metronomic chemotherapy (MCT) was administered to 100 patients (50.5%), demonstrating good tolerability, with 58 patients completing at least 75% of the scheduled cycles. Conclusion The implementation of a multicenter protocol incorporating MCT for metastatic ES proved feasible across Latin America.