Differentiation of radiographically indeterminate solitary pulmonary nodules with [F-18]fluoro-2-deoxyglucose positron emission tomography

Background: The purpose of this preliminary study was to evaluate the effic acy of positron emission tomography (PET) with [F-18]fluoro-2-deoxyglucose (FDG) for differentiating benign from malignant solitary pulmonary nodules. Methods: Twenty-six patients (12 females, 14 males, age 27-79 years) with r adiographically indeterminate solitary pulmonary nodules underwent FDG-PET and the findings were compared with the results of pathological examination of biopsy samples. FDG activity in the lesion was expressed as the ratio o f lesion-to-background counts (L/B ratio) for semiquantitative analysis. Results: The mean L/B ratio of malignant lesions (8.81 +/- 3.71, n = 20) wa s not significantly higher than that of benign lesions (4.71 +/- 3.00, n = 6) (p = 1.00). Using a cut-off L/B ratio of 5.0 for malignancy, FDG-PET cor rectly detected 19 true positive and three true negative cases, but failed to detect three false positive (two abscesses and one cryptococcus) cases a nd one false negative (adenocarcinoma) case. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 95, 50, 86, 75 and 85%, respectively. Conclusions: FDG-PET is a sensitive modality for detecting malignancy, but is not specific enough. Benign lung lesion with active inflammation could d emonstrate high FDG uptake, making it difficult to differentiate from malig nancy. In the future, we will increase the case numbers to evaluate further the utility of FDG-PET for differentiating radiographically indeterminate solitary pulmonary nodules.