The National Lung Screening Trial (NLST) was the first multicentered randomized controlled trial which showed that chest CT scans for early lung cancer detection in a high-risk population significantly reduced lung cancer mortality by 20% compared to a control group (1). Though these results were groundbreaking, 24% of all screening results were false positives; their definition for a positive outcome was the presence of a solid nodule ≥4 mm in diameter. Nine years after the NLST results were published, the Dutch-Belgian Lung Cancer Screening Trial (NELSON) reported a lung cancer mortality reduction of 24% and a false-positive rate to 2% (2). This false-positive reduction was achieved by volumetrically reassessing indeterminate nodules for growth instead of immediate referral to the pulmonologist. With nodule growth being the best visual predictor of malignancy, this implies that new nodules (not visible in prior scans) have a higher lung cancer probability than those found in the baseline scan (3). Han et al. (4) investigated the incidence of perifissural nodules (PFN) exclusively among new nodules detected in follow-up scans from the NELSON study.
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