Trends of lymph node sampling and metastasis in pediatric patients with clear cell, epithelioid, and synovial sarcomas

Abstract

Background: Clear cell sarcoma (CCS), epithelioid sarcoma, and synovial sarcoma are rare tumors historically identified as high risk for lymph node metastasis. Nodal metastasis in adults with these subtypes has been described. This study investigates incident nodal metastasis and associated survival in children with these subtypes. Procedure: Using the National Cancer Database (2004-2015), we created a retrospective cohort of 1303 patients (aged ≤25 years) who underwent local control therapy for CCS, epithelioid sarcoma, and synovial sarcoma. Kaplan-Meier curves estimated overall survival (OS) by subtype. Stratifying on subtype, Cox regressions assessed OS by lymph node sampling status and nodal metastasis. Results: There were 103 (7.9%) patients with CCS, 221 (17.0%) with epithelioid sarcoma, and 979 (75.1%) with synovial sarcoma. Lymph node sampling was more frequent in patients with CCS (56.3%) and epithelioid sarcoma (52.5%) versus synovial sarcoma (20.5%, p<0.001). Synovial sarcoma metastasized to lymph nodes less frequently than CCS or epithelioid sarcoma (2.2% vs. 14.6% and 15.0%, p<0.001). Across all subtypes, lymph node metastasis was associated with inferior OS (HR 2.10, CI 1.44-3.07, p<0.001). Lymph node sampling was associated with improved OS in CCS (HR 0.35, CI 0.15-0.78, p=0.010), inferior OS in synovial sarcoma (HR 1.60, CI 1.13- 2.25, p=0.007), and no statistical association with OS in epithelioid sarcoma. Conclusions: Lymph node metastasis is rare in children with synovial sarcoma. Lymph node sampling procedures were not consistently performed for patients with CCS or epithelioid sarcoma, but improved OS supports routine lymph node sampling in children with CCS.