Incidental findings on positron emission tomography/CT scans performed in the investigation of lung cancer

Abstract

This study aimed to clarify the number and cause of incidental findings detected on positron emission tomography (PET)/CT in patients undergoing investigation for presumed lung cancer. The scan reports from PET/CT studies performed for patients with lung cancer under National Institute for Clinical Evidence guidelines from January 2006 until March 2008 were retrospectively reviewed. Incidental findings were followed up by a combination of case note review, clinician feedback, colonoscopy database, histopathology and follow-up imaging. 818 patients were investigated for lung cancer in the study period. 197 incidental findings were found in 175 (21%) patients. The subsequent investigation of 108 lesions confirmed a pathological correlation in 71 (66%) cases. A second primary malignancy was found in 10 patients within the bowel (6), breast (2), tongue (1) and stomach (1). A pre-malignant lesion was confirmed in 25 cases (24 large bowel tubulovillous adenomas and a follicular thyroid lesion). A further 41 (5%) benign abnormalities were detected at multiple sites; the thyroid gland was the single most frequently affected site (14 abnormalities). There were 36 (4.4%) false-positive reported findings, including 17 in the region of the pharynx and larynx and 12 within the large bowel. Overall, 9.2% of patients with suspected or known lung cancer having PET/CT had a confirmed incidental finding. A malignant or pre-malignant lesion was found in 1.2% and 3.0%, respectively. These were mostly located within the gastrointestinal tract. The majority of false-positive incidental findings were located in the larynx and pharynx. Uptake in these regions is unlikely to be significant in the absence of a CT morphological correlation.