Impact of EBUS-TBNA on PET-CT Imaging of Mediastinal Nodes

Positron emission tomography-computed tomography (PET-CT) with fluorine-18-fluorodeoxyglucose has a high sensitivity in detecting malignancy in patients suspected of lung cancer but a low specificity as inflammatory reactions can also result in metabolic activity. Furthermore, it is assumed that invasive pulmonary procedures with biopsies from benign lesions can induce metabolic activity resulting in false-positive results. However, this hypothesis lacks solid evidence. We aimed to evaluate how often endobronchial ultrasound (EBUS) with biopsies from benign lesions are followed by false-positive results.

Patients with suspected or proven lung cancer admitted for invasive pulmonary procedures in a 6-year period were retrospectively reviewed. Patients who had at least 1 nonmalignant mediastinal lymph node (MLN) biopsied 1 to 13 days before PET-CT were included. The number of false-positive and true-negative results shortly after EBUS biopsy of nonmalignant MLN was reviewed.

Of 1025 patients, 216 patients were referred for PET-CT 1 to 13 days after biopsy. Of these, 107 patients had at least 1 MLN biopsied. From a total of 198 biopsied MLNs, we found 62% without metabolic activity (benign) and 38% with metabolic activity. In 5% the metabolic activity could be explained by an infection or inflammatory disorder, in 15% no cytologic follow-up was available, in 1% malignancy was confirmed at follow-up, and in 3% the patients were not possible to follow-up. In the remaining 14%, no other reasonable explanation for the metabolic activity was found other than the biopsy.

EBUS with biopsy do not necessarily result in PET activity. Therefore, PET-positive results should always be taken seriously, even when PET is performed shortly after biopsies.