Sparing Strategy Does Not Compromise Prognosis in Pediatric Localized Synovial Sarcoma: Experience of the International Society of Pediatric Oncology, Malignant Mesenchymal Tumors (SIOP-MMT) Working Group

Background: 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).

Procedure: 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).

Results: 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.

Conclusions: Only 32% of survivors received RT. OS was similar to published data. Omission of RT may be considered in younger children, to limit the potential sequelae in patients with tumors less than 5 cm in size initially submitted to marginal resection. This strategy may also be considered in initially unresected cases, when the tumor is resected at delayed surgery with microscopically free margins, and in patients in complete remission after primary chemotherapy.