Postoperative prognostic assessment using ECV fraction derived from equilibrium contrast-enhanced CT in thymomas

To assess the postoperative prognostic utility of extracellular volume (ECV) fraction measurement using equilibrium contrast-enhanced CT (CECT) in patients with thymomas. Enrolled in the study were patients with thymomas who were assessed by pretreatment CECT. ECV fraction was determined from measurements within the lesion and aorta on unenhanced and equilibrium phase CECT. Masaoka-Koga stage, WHO histological classification, and morphological features on CT including tumor size and boundary clarity were also evaluated. Univariate and bivariate analyses using Cox proportional hazards regression model were performed to evaluate the factors affecting recurrence-free survival (RFS). RFS rates were analyzed using the Kaplan-Meier method. A total of 100 consecutive patients (52 low-risk and 48 high-risk thymomas) were enrolled in this study. Bivariate analyses identified boundary, Masaoka-Koga stage, and ECV fraction as independent significant variables for predicting RFS across all parameters. Mean RFS was significantly shorter in the group with ill-defined boundary (ill-defined, 102.5 months; well-defined, 167.4 months; p < 0.001), high Masaoka-Koga stage (stage 3 or 4, 54.9 months; stage 1 or 2, 164.2 months; p < 0.001), and high ECV fraction (ECV fraction ≥ 27.5 %, 110.3 months; ECV fraction < 27.5 %, 170.1 months; p < 0.001). ECV fraction derived from equilibrium CECT was an independent risk factor for RFS in patients with thymoma.