['The aim of this analysis was to identify if the modified indications of radiotherapy (RT) or radical surgery compromised survival in pediatric synovial sarcoma (SS).', 'Children with non-metastatic SS, prospectively enrolled in three trials, were analyzed. After primary surgery or biopsy, they received chemotherapy. RT was planned after chemotherapy in patients who had not achieved a complete response (CR). The considered outcome was 5-year overall survival (OS) and event-free survival (EFS).', 'Eighty-eight patients were identified. Primary tumors were mainly located in limbs (66%). The first-line therapy for 65 patients was primary resection. Of the 49 patients who had gross tumor resection, 43 received adjuvant chemotherapy, and 8 had RT. All of the 39 patients with macroscopic residual disease received chemotherapy, then only surgery (n = 12) ± RT (n = 22). The 5-year EFS and OS rates were 68% and 85%, respectively. The TNM stage was a prognostic factor for relapse, whereas primary site of the tumor and TNM stage were prognostic factors for death.'] Does sparing strategy compromise prognosis in pediatric localized synovial sarcoma : experience of the International Society of Pediatric Oncology , Malignant Mesenchymal Tumors ( SIOP-MMT ) Working Group?