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 b iopsy are unsuccessful or are falsely reassuring, and the decision to send the patient for more invasive and potentially morbid procedures can be diff icult. Our aim was to investigate the role of fluorine-18 fluorodeoxyglucos e positron emission tomography (FDG-PET) in helping to identify more accura tely those patients with malignant lesions. Sixty-three patients underwent FDG-PET scans following unsuccessful biopsy of a lung lesion or, in a lesse r number of cases, when an attempt at biopsy was considered too dangerous. Follow-up was by histology or, if this was unavailable, by clinical progres s to death or a minimum of 18 months post scan. Visual and quantitative ana lysis was performed. On visual analysis, positive and negative predictive v alues 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 patien ts in this circumstance is non-invasive and highly sensitive in diagnosing malignancy. The high positive predictive value suggests that those with a p ositive scan must undergo further investigation, while the 100% negative pr edictive value means those with no FDG uptake can safely be spared further invasive investigations.