Early experience with PET scanning in thoracic tumours

Background. Positron emission tomography (PET) scan is an imaging technique which relies on metabolic properties of the lesions. In this study, we evaluated the potential contribution of PET for thoracic malignancy in a consecutive series of patients presenting with multiple lesions or equivocal diagnosis. Methods. PET with 2-18 F fluorodeoxyglucose (FDG) was carried out in 41 patients. The diagnosis was primary intrathoracic malignancy in 22 (Group 1). On routine staging using CT scan we found 29 additional lesions and assessed these using PET scan. PET was performed to evaluate the number of metastatic lesions in the lung in 11 (Group 2), to characterise undiagnosed pathology in the chest in 4 (Group 3), to search clinically suspicious extrathoracic spread in 4 patients with known intrathoracic malignancy. Results. In Group 1, the sensitivity and specificity of PET was 81.2% and 92.3%. The accuracy of PET in the confirmation of metastatic disease to the chest was 73%. PET was falsely positive in a patient with chronic inflammatory disease in Group 3 and highly accurate to characterise unknown pathology in Group 4. Conclusions. Even though infection may cause false positive results, PET is a useful imaging technique for the evaluation of patients with thoracic tumours.