Intratumoral metabolic heterogeneity by 18 F-FDG PET/CT to predict prognosis for patients with thymic epithelial tumors

The aim of the present study was to evaluate the impact of intratumoral metabolic heterogeneity and quantitative F-FDG PET/CT imaging parameters in predicting patient outcomes in thymic epithelial tumors (TETs). This retrospective study included 100 patients diagnosed with TETs who underwent pretreatment F-FDG PET/CT. The maximum and mean standardized uptake values (SUVmax and SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) on PET/CT were measured. Heterogeneity index-1 (HI-1; standard deviation [SD] divided by SUVmean) and heterogeneity index-2 (HI-2; linear regression slopes of the MTV according with different SUV thresholds), were evaluated as heterogeneity indices. Associations between these parameters and patient survival outcomes were analyzed. The univariate analysis showed that Masaoka stage, TNM stage, WHO classification, SUVmax, SUVmean, TLG, and HI-1 were significant prognostic factors for progression-free survival (PFS), while MTV, HI-2, age, gender, presence of myasthenia gravis, and maximum tumor diameter were not. Subsequently, multivariate analyses showed that HI-1 (p