Primary Site and Other Prognostic Variables Effects on Survival in Pediatric Synovial Sarcoma

Abstract

Background: Synovial sarcomas (SS) are an aggressive type of soft tissue sarcoma that represent 10% of soft tissue sarcomas. Patients under the age of 20 represent 30% of all SS, and while pediatric and adult patients with SS have similar clinical presentations, pediatric cases have improved outcomes. Prognostic factors include tumor size, primary site, and presence of distant metastases. Methods: 597 pediatric (<18 years old) patients diagnosed with SS from the National Cancer Database were analyzed. Kaplan-Meier tables were compiled to estimate 1-, 3-, 5-, and 10-year survivals. Groups were compared using log-rank tests and Cox proportional hazards analysis. Results: Median age at diagnosis was 14 years, 79.4% of patients were Caucasian, and median tumor size was 6.0 cm. The most common anatomical primary site was the extremities, specifically the lower limb and hip. Overall 5- and 10-year survival probabilities were 85.3% and 79.5%, respectively. Tumors in the lungs and thorax had the worst survival, with an overall 5-year survival probability of 50.2%, while upper limb and shoulder tumors had the best 5-year survival probability of 95.9%. The 6-10 age range had the best 5- and 10-year survival probabilities and as age increased the overall survival decreased. Pediatric females had better survival outcomes than males. Approximately 91% of pediatric SS did not present with metastases but the most common site of metastasis was the lungs (2.8%). As histologic grade and tumor stage increased, survival decreases, except that stage II disease showed the best 5-year survival. Biphasic histology had better 5- and 10-year survival outcomes when compared to monophasic histology. Conclusion: This is the largest and most comprehensive study on pediatric SS to date. Statistically significant prognostic variables of pediatric SS include primary anatomical site, sex, race, histology type, tumor size, and histologic grade and stage.