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.