The Results of Radiotherapy in Childhood Neuroblastomas: Turkish Society for Radiation Oncology- Pediatric Tumors Study Group Melis Gültekin1, Gizem Coşgun2, Ayşe Nur Demiral3, Zeynep Ağmaç4, Cem Uzal5, Melek Tuğçe Yılmaz1, Yavuz Anacak2, Fulya Ağaoğlu4, Nur Olgun6, Serap Aksoylar7, Canan Akyüz8, Murat Gürkaynak1, Ferah Yıldız1, Serra Kamer2 1Hacettepe University Faculty of Medicine, Department of Radiation Oncology, 2Ege University Faculty of Medicine, , Department of Radiation Oncology, 3Dokuz Eylul University Faculty of Medicine, Department of Radiation Oncology, 4Acıbadem Mehmet Aydinlar University Faculty of Medicine, Department of Radiation Oncology, 5Trakya University Faculty of Medicine, Department of Radiation Oncology, 6Dokuz Eylul University Faculty of Medicine, Department of Pediatric Oncology, 7Ege University Faculty of Medicine, Department of Pediatric Oncology, 8Hacettepe University Faculty of Medicine, Department of Pediatric Oncology OBJECTIVES: In this multicentric retrospective analysis, we evaluated the oncologic outcome of patients with neuroblastoma (NBL) who were treated with radiotherapy (RT) in addition to systemic chemotherapy and surgery. RESULTS: Median age: 42 mos (range, 5-156 mos) 41% female and 59% male Median LDH level: 900 U/L IR group: n=14 (12%) HR group: n=102 (88%) Metastatic disease: n=75 (65%) Median follow-up: 38 mos (range, 4-174 mos) Forty-two patients (36%) were alive without disease, 19 patients (16%) were alive with disease, and 31 (27%) patients died due to progression. Two (2%) cases had isolated local recurrence, 1 (1%) had regional recurrence, 6 (5%) were with local-regional recurrence, and 26 (22%) were with distant metastases. The 2- and 5-year overall survival (OS) rates were 86% and 69%, and the progression-free survival (PFS) rates were 64% and 53%, respectively. The LDH level (1500 vs. ≥1500 U/L) and the presence of metastasis at diagnosis were found to be significant prognostic factors for OS and PFS. Grade 3 hematological toxicity developed in 4 (3%) cases during RT. In the long-term follow-up, 7 (6%) patients had hypoplasia/atrophy on the same kidney. MATERIALS AND METHODS: 116 patients 05/2004 - 01/2018 Turkish Pediatric Oncology Group (TPOG) 2003 (21%) and 2009 (75%) protocol GTV 30Gy, CTV 25.5 Gy 110 (95%) primary tumor bed and lymphatic region 6 (5%) + metastatic foci CONCLUSIONS: Multidisciplinary intensive treatment should have applied in the treatment of NBL, especially in the cases of HR disease. RT provides effective local control in the primary tumor site. Long-term follow-up is necessary to evaluate treatment-related complications. Serra Kamer, MD Ege University Faculty of Medicine, Department of Radiation Oncology serra.kamer@ege.edu.tr