Prognostic Significance of Metabolic Parameters by (18)F-FDG PET/CT in Thymic Epithelial Tumors

SIMPLE SUMMARY: Thymic epithelial tumors have variable prognoses that depend on histological subtype, and (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) currently plays an important part in oncology images. Thus, we prosecuted a retrospective review of data from 83 patients with thymic epithelial tumors who underwent pretreatment (18)F-FDG PET/CT and investigated the prognostic significance along with WHO classification, Masaoka stage, and volumetric (18)F-PET parameters. Masaoka stage, histologic type, treatment modality, maximum standardized uptake values (SUV(max)), average standardized uptake values (SUV(avg)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were significant prognostic factors for time-to-progression on univariate survival analysis. On multivariate analysis, SUV(avg) and Masaoka stage were important independent prognostic factors for progression-free survival in thymic epithelial tumors. ABSTRACT: Background: Imaging tumor FDG avidity could complement prognostic implication in thymic epithelial tumors. We thus investigated the prognostic value of volume-based (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT parameters in thymic epithelial tumors with other clinical prognostic factors. Methods: This is a retrospective study that included 83 patients who were diagnosed with thymic epithelial tumors and underwent pretreatment (18)F-FDG PET/CT. PET parameters, including maximum and average standardized uptake values (SUV(max), SUV(avg)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG), were measured with a threshold of SUV 2.5. Univariate and multivariate analysis of PET parameters and clinicopathologic variables for time-to-progression was performed by using a Cox proportional hazard regression model. Results: There were 21 low-risk thymomas (25.3%), 27 high-risk thymomas (32.5%), and 35 thymic carcinomas (42.2%). Recurrence or disease progression occurred in 24 patients (28.9%). On univariate analysis, Masaoka stage (p < 0.001); histologic types (p = 0.009); treatment modality (p = 0.001); and SUV(max), SUV(avg), MTV, and TLG (all p < 0.001) were significant prognostic factors. SUV(avg) (p < 0.001) and Masaoka stage (p = 0.001) were independent prognostic factors on multivariate analysis. Conclusion: SUV(avg) and Masaoka stage are independent prognostic factors in thymic epithelial tumors.