Abstract
This study aims to clarify the impact of tumor size on the prognosis of patients diagnosed with thymoma and thymic carcinoma, leveraging data from a population-based registry. Utilizing the SEER database, this retrospective analysis identified patients diagnosed with thymoma and thymic carcinoma from 2000 to 2020. Propensity score matching was employed to mitigate potential statistical biases between groups categorized by tumor size (≤ 6.5 cm and > 6.5 cm). The study included a total of 3857 patients, comprising 2688 with thymoma and 1169 with thymic carcinoma. Multivariate analysis demonstrated that tumors ≤ 6.5 cm independently correlated with improved Cancer-Specific Survival (CSS) (p = 0.001; p < 0.001) and Overall Survival (OS) (p < 0 .001; p < 0.001) in both thymoma and thymic carcinoma cohorts. Subgroup analysis revealed that smaller tumors (≤ 6.5 cm) conferred survival benefits in patients with Masaoka-Koga stage IIB thymomas and stage III/IV thymic carcinomas (thymoma: CSS: p < 0.0001; OS: p = 0.00045; thymic carcinoma: CSS: p = 0.028; OS: p = 0.014). Additionally, WHO type A/AB/B1 and type B2/B3 thymomas with tumors ≤ 6.5 cm exhibited superior CSS (p = 0.005; p < 0.00018) and OS (p = 0.015; p = 0.0021). Through propensity matching analysis utilizing the SEER database, this study underscores the prognostic significance of tumor size in both early-stage thymoma and advanced-stage thymic carcinoma, identifying a critical threshold of 6.5 cm. In the WHO classification, tumor size based on the cut-off value of 6.5 cm has a greater impact on the prognosis of type B2/B3 (high-risk group) than A/AB/B1 (low-risk group).