Surgery in Masaoka stage IV thymic carcinoma: a propensity-matched study based on the SEER database

BACKGROUND: Thymic carcinoma is a type of rare and highly malignant tumor. Limited information was available on prognostic factors of late-stage thymic carcinoma. The aim of this study was to identify factors that impact prognosis and to define the relationship between survival and surgical intervention in patients with Masaoka stage IV thymic carcinoma. METHODS: From 1973 to 2015, a total of 311 consecutive patients were enrolled in this study with pathologic confirmed Masaoka stage IV thymic carcinoma from the Surveillance, Epidemiology, and End Results database. Kaplan-Meier analyses, Cox-regression analyses and propensity score matching (PSM) were performed to evaluate prognosis. RESULTS: In the multivariate analysis, larger tumor size, distant metastasis and positive lymph node status were associated with poorer outcome. After PSM, no receipt of surgery was the prognostic factor indicating poorer survival [hazard ratio (HR) 1.985, 95% confidence interval (CI) 1.007–3.913, P=0.048 for overall survival (OS); HR 1.649, 95% CI: 1.009–2.697, P=0.046 for disease-specific survival (DSS)]. Subgroup analysis indicated that significantly improved survival with surgery was observed in patients who were