Positron emission tomography in pulmonary masses where tissue diagnosis is unhelpful or not possible

Objective: To document the usefulness of positron emission tomography (PET) in diagnosing lung masses where tissue diagnosis is not possible or is unhelpful. Design: Cohort study (partly retrospective). Setting: Departments of positron emission tomography and diagnostic imaging of a tertiary referral dedicated cancer hospital in Melbourne. Patients: 40 of 60 consecutive patients referred for evaluation of an indeterminate lung nodule or mass, comprising 15 in whom biopsy was not possible and 25 in whom biopsy had either failed or did not confirm malignancy or a specific benign diagnosis. Main outcome measures: Accuracy of blinded reading of PET scans in determining whether the lung lesion is benign or malignant (final diagnosis established either through surgical biopsy or from long term clinical and imaging follow-up). Results: PET yielded 23 true positives, 13 true negatives, 3 false positives (2 tuberculosis, 1 sarcoidosis) and 1 false negative (an adenocarcinoma), giving a sensitivity of 96%, a specificity of 81%, a negative predictive value of 93%, and a positive predictive value of 88% (for malignancy). Conclusions: For lung nodules where tissue diagnosis was not possible or was unhelpful, the negative predictive power of PET was sufficiently high to avoid open biopsy, and to follow such patients with serial surveillance. On the other hand, most lesions that were positive on PET were either malignant or required specific active management determined from histological characterisation. PET therefore contributed to improved patient management and has reduced the need for open thoracotomy.