Localized Synovial Sarcoma: A Population-Based Analysis of Treatment Patterns and Survival.

Purpose: Synovial sarcoma (SS) is a rare, high-grade soft tissue tumor that requires multidisciplinary and multimodal care with surgery, radiotherapy, and chemotherapy. We examined the impact of sociodemographic and clinical factors on treatment patterns and survival in localized SS patients. Methods: Adolescents and young adults (AYAs, 15-39 years) and older adults ("adults," ≥40 years) diagnosed with localized SS from 2000 to 2018 were identified in the California Cancer Registry. Multivariable logistic regression identified clinical and sociodemographic factors associated with receipt of chemotherapy and/or radiotherapy. Cox proportional hazards regression identified factors associated with overall survival (OS). Results are reported as odds ratios (ORs) and hazard ratios (HRs), respectively, with 95% confidence intervals (CIs). Results: More AYAs ( n  = 346) than adults ( n  = 272) received chemotherapy (47.7% vs. 36.4%) and radiotherapy (62.1% vs. 58.1%). Age at diagnosis, tumor size, treatment at National Cancer Institute-Children's Oncology Group (NCI-COG)-designated facilities, insurance status, and neighborhood socioeconomic status (SES) influenced treatment patterns. Among AYAs, treatment at NCI-COG-designated facilities was associated with receiving chemotherapy (OR 2.74, CI 1.48-5.07) and low SES was associated with worse OS (HR 2.28, 1.09-4.77). In adults, high SES was associated with receiving chemoradiotherapy (OR 3.20, CI 1.40-7.31), whereas public insurance was associated with decreased odds of chemoradiotherapy (OR 0.44, CI 0.20-0.95). With regard to treatment, absence of radiotherapy (HR 1.94, CI 1.18-3.20) was associated with worse OS in adults. Conclusion: In localized SS, both clinical and sociodemographic factors influenced treatment patterns. Further research should investigate how SES-related factors produce treatment disparities and identify interventions to improve treatment equity and outcomes.