FDG-PET as a "metabolic biopsy" tool in thoracic lesions with indeterminate biopsy

A common problem encountered in clinical medicine is the classification of a lung lesion (nodule/opacity) on conventional imaging. Often attempts at biopsy are unsuccessful or are falsely reassuring, and the decision to send the patient for more invasive and potentially morbid procedures can be difficult. Our aim was to investigate the role of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in helping to identify more accurately those patients with malignant lesions. Sixty-three patients underwent FDG-PET scans following unsuccessful biopsy of a lung lesion or, in a lesser number of cases, when an attempt at biopsy was considered too dangerous. Follow-up was by histology or, if this was unavailable, by clinical progress to death or a minimum of 18 months post scan. Visual and quantitative analysis was performed. On visual analysis, positive and negative predictive values were 90% and 100%, respectively. On quantitative (SUV >2.5) analysis, positive and negative predictive values were 90% and 85%, respectively. We interpret these results as showing that the use of FDG-PET scans in patients in this circumstance is non-invasive and highly sensitive in diagnosing malignancy. The high positive predictive value suggests that those with a positive scan must undergo further investigation, while the 100% negative predictive value means those with no FDG uptake can safely be spared further invasive investigations.