Abstract
1930
Objectives There are only limited numbers of reports showing the usefulness of FDG-PET in thymic epithelial tumors. The purpose of our study was to assess the usefulness of dual-phase F-18 FDG-PET/CT for various subtypes of thymic epithelial tumors defined by World Health Organization classification.
Methods Thirty patients with histologically verified thymic epithelial tumors [12 with low-risk thymomas (type A, type AB and type B1), 9 with high-risk thymomas (type B2, type B3), and 9 thymic cancer] were enrolled in this study. All patients were underwent early scan at after 1 hour and delayed scan at 2 hours after FDG injection. The maximum standardized uptake value of the tumor at the early scan (eSUVmax) and that at the delayed scan (dSUVmax) were measured, and the retention index [(dSUVmax-eSUVmax)/eSUVmax] was calculated.
Results The eSUVmax of low-risk thymomas (4.92±3.15) and that of high-risk thymomas (4.92±1.63) were significantly lower than that of thymic cancers (9.02±3.49). The dSUVmax of low-risk thymomas (5.70±4.00) and that of high-risk thymomas (5.17±2.41) were also significantly lower than that of thymic cancers (10.69±4.68). The dSUVmax was higher than the eSUVmax in all types of thymic tumors. However, there was no significant difference in the retention indexes among low-risk thymomas (11.95±11.88%), high-risk thymomas (6.61±15.41%) and thymic cancers (17.53±8.52%).
Conclusions Both eSUVmax and dSUVmax were useful for differentiation of thymic cancer from other types of thymic tumors. Although it seems the delayed scan has no additional value over the early scan in terms of the diagnostic performance, it still has clinical value because of the stronger FDG uptake in the tumor