The impact of margins and re-resection in pediatric synovial sarcoma

Introduction: Synovial sarcoma is one of the most common soft tissue sarcomas in children. Guidelines regarding the adequate extent of resection margins and the role of reresection are lacking. We sought to evaluate the adequate resection margin and the role of reresection in predicting outcomes in children with synovial sarcomas. Methods: A cohort of 36 patients less than 18 years of age at diagnosis who were treated for localized synovial sarcoma at three tertiary pediatric hospitals between January 2004 and December 2020 were included in this study. Patient and tumor demographics, treatment information, and margin status after surgical resection were collected from the medical record. Clinical, treatment, and surgical characteristics, as well as outcomes including hazard ratios (HRs), event- free survival (EFS), and overall survival (OS) were compared by resection margins group and reresection status. Results: Patients in the R1 resection group were significantly more likely to relapse or die compared to patients in the R0 resection group. However, there was no significant difference in EFS (HR 0.52, p = 0.54) or OS (HR 1.56, p = 0.719) in R0 patients with less than 5 mm margins compared to R0 patients with more than 5 mm margins. Patients with R1 on initial or reresection had significantly worse OS than patients who had R0 resection on initial or re- resection (HR = 10.12, p = 0.005). Conclusion: This study re- affirms that R0 resection is an independent prognostic predictor of better OS/EFS in pediatric synovial sarcoma. Second, our study extends this finding to report negative margins on initial resection or re- resection is associated with better OS/EFS than positive margins on initial resection or re- resection. Lastly, we found that there is no difference in outcomes associated with re- resection or < 5 mm margins for R0 patients, indicating that re- resection and < 5 mm margins are acceptable if microscopic disease is removed.