Incidental lung nodules are problematic. Their detection generates 2 years of CT scan follow-up, causing patient anxiety, immense cost and a high radiation burden. Few of these nodules are malignant. The 2005 Fleischner society guidelines are complex with no reference to the value of PET- CT imaging.
The Sheffield Teaching Hospital Trust follows a modified Fleischner protocol where the majority of patients have 3 follow-up scans over 2 years. This study aimed to:
Determine the final diagnosis of each nodule and the number of follow-up CT scans performed.
Asses the value of PET-CT nodule imaging.
Determine whether an experienced chest radiologist could predict which nodules were malignant/ benign by CT characteristics alone.
Pulmonary nodules under review were extracted from the Trust lung cancer database. The final diagnoses were determined after 2 + years of follow up. An experienced chest radiologist reviewed all the nodules, recording their impression of whether the nodules were benign/ malignant.
162 nodules in 140 patients were analysed. Six patients were excluded as no follow up data. 148\156 nodules were benign (95%), 7 malignant and one presumed malignant (had inadequate follow-up). The 140 patients had 427 scans follow-up CT scans (mean 2.7, mode 3). 47 patients had fewer scans than required by protocol due to eg nodule resolution (9), recommendation to stop follow-up on CT report (13) and diagnosis of other disease (11). 20/22 patients had 4 + follow-up scans due to shortened time interval between scans.
35 patients had PET CT scan. 28/29 nodules with low FDG uptake were morphologically benign and stable at 2 years. 1 “cold” nodule with malignant morphology was resected (adenocarcinoma).
The analysis of lung nodules by experienced chest radiologist found NPV 97.6%, PPV 15%, specificity 81% and sensitivity 62.5%.
Comment The vast majority of lung nodules followed-up were benign. Better use of CT nodule morphology and review by an experienced chest radiologist is advised. We recommend that patients with a “cold”, morphologically benign, nodule on PET-CT scan should have a single 12 month CT scan to confirm stability.
H MacMahon, et al. Radiology 2005;237:395–400.
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