Evolving treatment strategies and the impact of centralization on outcomes in thymic epithelial tumors: A nationwide population-based study from the Netherlands

INTRODUCTION: Thymic epithelial tumors (TETs) are rare malignancies with heterogeneous histology, clinical presentation, and outcomes. Although clinical guidelines have remained largely unchanged, the management of TETs has evolved through advances in staging, radiotherapy and surgical techniques. This study describes the population of TET patients in the Netherlands diagnosed between 2017 and 2024 and aims to evaluate trends in incidence, treatment patterns, and outcomes, with particular attention to differences between high- and low-volume centers. METHODS: All patients with a new diagnosis of TET between 2017 and 2024 were identified from the Netherlands Cancer Registry database. Poisson regression, chi-square test, logistic regression and Cox-hazard models were used for analysis. A high-volume center was defined as performing > 10 TET surgeries a year. RESULTS: In total, 1083 patients were included of whom 81,3% had thymoma and 15,5% thymic carcinoma. The overall crude incidence was 7.3 per 1000,000 with a rising trend over time. Chemotherapy was administered in 17,5% of patients and radiotherapy in 16,3%. Surgery was performed in 75,3% of patientswith a shift from open to robotic-assisted thoracoscopic surgery as the preferred approach. Among operated patients, 9,7% received postoperative radiotherapy. Complete resection (R0) was achieved in 84,4% of resections and was associated with improved survival (p = 0.003). Surgery for TET was performed across 25 different centers in the Netherlands. High-volume centers performed more robotic procedures and achieved higher R0 resection rates compared with low-volume centers. CONCLUSION: The incidence of TETs in the Netherlands increased and treatment strategies evolved over time. Complete resection remains the most important prognostic factor for survival. High-volume centers achieved higher rates of R0 resection, strongly supporting further centralization of TET care, including centralization of surgery.