Conflicting or complementary role of computed tomography (CT) and positron emission tomography (PET)/CT in the assessment of thymic cancer and thymoma

Purpose: To evaluate the role of CT and PET/CT in thymic cancer and thymoma patients at initial staging. Methods and Materials: We retrospectively reviewed CT and PET/CT of 26 patients with a proven-diagnosis of thymic cancer (n=9)and thymoma (n=17).Chest CT findings documented were qualitative (calcification, peritumoral fat infiltration,pleural-pericardial effusion, degree of abutment of vessel circumference, et al)and quantitative (maximum axial and longitudinal diameter and volume).Both qualitative and semiquantitative data (standardised uptake value, total lesion glicolysis-TLG, metabolic tumor volume-MTV)were recovered by PET/CT.The outcome of all patients was retrieved by clinical chart or observational follow-up.The comparisons among histological entities, outcome and CT and PET/CT findings were evaluated using a non-parametric analysis. Results: PET/CT resulted positive in 15 patients with thymoma.100%of patients with thymic cancer had a positive scan.CT was available in 5/9 patients with thymic cancer and in 3/17 subjects with thymoma.All quantitative CT parameters were significantly higher in patients with thymic cancer than thymoma (MAD:45vs.20 mm,MLD:69vs.21 mm and volume:77.91vs.4.52 ml;all p < 0.05).Conversely, only MTV and TLG were significantly different in patients with thymic cancer than the counterpart (126.53vs.6.03 cm3 and 246.05vs.20.32,respectively;both p < 0.05).After a median follow-up of 17.45 months, four recurrences of disease occurred (three in patients with thymic cancer and one with a type B2 thymoma).Follow-up data were lost in three subjects.CT volume in a patient with recurrent disease was 170.12 ml vs. a median value of 10.5 ml in seven disease-free patients.MTV was higher in recurrent than disease-free subset (143.3vs.81.13 cm3),although not statistically significant (p=0.075). Conclusion: Both morphological and metabolic volume can be useful for diagnostic and prognostic meaning in thymic cancer and thymoma patients.