Value of 18F-FDG PET/computed tomography in predicting the simplified WHO grade of malignancy in thymic epithelial tumors.

Abstract

To investigate the value of 18F-fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) in predicting the simplified WHO grade of malignancy in thymic epithelial tumors. We retrospectively reviewed 81 patients with pathologically proven thymic epithelial tumors who underwent F-FDG PET/CT before surgical resection. Maximum standardized uptake value (SUVmax) and SUVmax/tumor size were measured on the primary lesion. A receiver operating characteristics (ROC) curve were performed for assessing the ability of F-FDG PET/CT as a predictor of the simplified WHO classification. There were 43 male patients (53.1%) and 38 female patients (46.9%), and the mean age was 55.6 ± 11.9 years. The mean tumor size was 53.2 ± 21.4 mm. There were 24 low-risk thymomas (29.6%) (A, AB, and B1), 29 high-risk thymomas (35.8%) (B2 and B3), and 28 thymic carcinomas (34.6%). The SUVmax and SUVmax/tumor size were found to be predictive factors that were useful to distinguish thymomas and thymic carcinomas, and area under the ROC curve were 0.820 and 0.691, respectively (P < 0.05), and the cutoff value for discriminating thymomas and thymic carcinomas was 5.34. In conclusion, a significant relationship was observed between SUVmax, SUVmax/tumor size and histological WHO classification of thymic epithelial tumors. F-FDG PET/CT may be useful for predicting the grade of malignancy in thymic epithelial.