Objectives: Positron emission tomography using [(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG-PET) plays an important role in many oncological settings. In this study, we assessed the utility of (18)F-FDG PET-CT for predicting the histologic type and stage of thymic epithelial tumours.
Methods: We retrospectively analyzed 58 patients with thymic epithelial tumours who underwent PET-CT before treatment and investigated the relationship between the histologic type based on the World Health Organization classification and the maximum standardized uptake value (SUV(max)) of each tumour. We also analyzed the relationship between the Masaoka tumour stage and the SUV(max).
Results: The study included 31 males and 27 females, ranging in age from 25 to 80 years (median: 62 years). The tumour histology of 44 tumours was thymoma and that of the remaining tumours was thymic carcinoma, including 11 squamous cell carcinomas and 3 carcinoids. The Masaoka tumour stage was as follows: Stage I in 8, Stage II in 24, Stage III in 18 and Stage IV in 8 patients. The patients were divided into three groups according to a simplified histologic classification: low-risk thymomas (types A, AB and B1, n = 23), high-risk thymomas (types B2 and B3, n = 21) and thymic carcinomas (n = 14). The SUV(max) of the thymic carcinoma group was significantly higher than those of the low-risk thymoma and high-risk thymoma groups (P < 0.001, respectively). No significant differences between the low-risk thymoma and high-risk thymoma groups were observed (P = 0.204). The SUV(max) of Stages III and IV thymomas showed a higher trend toward Stages I and II thymomas (P = 0.060).
Conclusions: PET-CT is a useful modality for predicting the histologic type and tumour stage of thymic epithelial tumours.