Tumor Size as a Prognostic Factor in Limited-Stage Thymic Epithelial Tumors: A Multicenter Analysis

Abstract Objectives The prognostic significance of tumor size in thymic epithelial tumors (TETs) has not been fully evaluated. We aimed to clarify the prognostic value of tumor size in limited-stage and advanced-stage TETs. Methods Clinical records of patients with completely resected TETs were retrospectively collected from four tertiary centers between January 2000 and February 2013. Information on the Masaoka–Koga stage was available for 1,215 patients (M-K group), and 433 patients were classified according to the eighth edition of the Tumor-Node-Metastasis (TNM) staging system (TNM group). Limited-stage and advanced-stage TETs were defined according to whether they were confined within the surrounding fatty tissues without invasion. The optimal cutoff value was selected using a maximally selected log-rank statistic. Results The median tumor size was 6.0 ± 2.8 cm in the M-K group and 6.5 ± 3.0 cm in the TNM group. In the multivariable analysis, tumor size had a significant effect on both overall survival (OS) (p = 0.003) and recurrence-free survival (RFS) (p 5.5 cm for both OS and RFS in limited-stage TETs. Conclusions Tumor size is an independent prognostic factor in patients with completely resected limited-stage TETs and a cutoff value of >5.5 cm might help clinicians enact proper treatment strategies and surveillance.