Synovial sarcoma in children and adolescents: the European Pediatric Soft Tissue Sarcoma Study Group prospective trial (EpSSG NRSTS 2005).

BACKGROUND: To report the results of the first European prospective nonrandomized trial dedicated to pediatric synovial sarcoma. PATIENTS AND METHODS: From August 2005 to August 2012, 138 patients <21 years old with nonmetastatic synovial sarcoma were registered in 9 different countries (and 60 centers). Patients were treated with a multimodal therapy including ifosfamide-doxorubicin chemotherapy and radiotherapy, according to a risk stratification based on surgical stage, tumor size and site, and nodal involvement. RESULTS: With a median follow-up of 52.1 months (range 13.8-104.4 months), event-free survival (EFS) was 81.9% and 80.7%, and overall survival (OS) was 97.2% and 90.7%, at 3 and 5 years, respectively. The only significant prognostic variable at univariate analysis was the risk group: 3-year EFS was 91.7% for low-risk, 91.2% for intermediate-risk, and 74.4% for high-risk cases. In 24 low-risk patients (completely resected tumor ≤5 cm in size) treated with surgery alone, there were two local relapses and no metastatic recurrences. Among 67 high-risk patients (unresected, or axial tumor or nodal involvement), 66 underwent surgery after neoadjuvant chemotherapy. Response to chemotherapy was 55.2%, including 22.4% cases with complete or major partial remissions, and 32.8% with minor partial remissions. CONCLUSION: This study demonstrates that collaborative prospective studies on rare pediatric sarcomas are feasible even on a European scale, with excellent treatment compliance. The overall results of treatment were satisfactory, with higher survival rates than those previously published by pediatric groups. Nonetheless, larger, international projects are needed, based on a cooperative effort of pediatric and adult oncologists. CLINICAL TRIALS NUMBER: European Union Drug Regulating Authorities Clinical Trials No. 2005-001139-31.