Low-Dose CT Screening: New Solid Nodules and Lung Cancer Probability

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As reported by Walter et al in The Lancet Oncology, incidence screening with low-dose computed tomography (CT) in high-risk individuals detected new solid nodules in approximately 5% to 7% at second and third screenings in the ongoing Dutch-Belgian NELSON trial. Larger nodule size was associated with a greater risk for lung cancer. Matthijs Oudkerk, PhD, of the University Medical Center Groningen, is the corresponding author of the article.

Study Details

In the trial, 15,822 participants who had smoked at least 15 cigarettes/d for > 25 years or at least 10 cigarettes/d for > 30 years and were current smokers or had quit smoking < 10 years ago were randomly assigned between December 2003 and July 2006 to receive low-dose CT screening (n = 7,915) or no screening (n = 7,907). A total of 7,557 individuals had baseline screening, and 7,295 had second and third (incidence) screening rounds.

The analysis included all participants with solid noncalcified nodules defined as new or < 15 mm³ at previous screens. Diagnosis of lung cancer was based on histology; the benign status of lesions was based on histology or stable size for at least 2 years. In baseline screening, 70 of 7,557 participants (1%) were diagnosed with lung cancer.

New Solid Nodules

In the second and third screening rounds, 1,222 new solid nodules were identified in 787 participants (11%); detection rates were 5% in the second and 7% in the third round. Among these 787 participants, a new solid nodule was diagnosed as lung cancer in 49 subjects (6%).

Overall, 50 lung cancers were found, representing 4% of all new solid nodules. Among lung cancer cases, 34 (68%) were diagnosed at stage I. Overall, 200 of 7,582 participants (3%) were diagnosed with lung cancer during the first three screening rounds.

Nodule Volume and Cancer Risk

Nodule volume had a high discriminatory power for lung cancer diagnosis (area under the receiver operating curve = 0.795, P < .0001). Lung cancer was diagnosed for 2 of 417 nodules < 27 mm³ (0.5%, 95% confidence interval [CI] = 0.0%–1.9%), 17 of 542 nodules of 27 mm³ to 206 mm³ (3.1%, 95% CI = 1.9%–5.0%), and 29 of 172 nodules ≥ 206 mm³ (16.9%, 95% CI = 12.0%–23.2%). A volume cutoff value of ≥ 27 mm³ was associated with > 95% sensitivity for lung cancer.

The investigators concluded: 

Our study shows that new solid nodules are detected at each screening round in 5%–7% of individuals who undergo screening for lung cancer with low-dose CT. These new nodules have a high probability of malignancy even at a small size. These findings should be considered in future screening guidelines, and new solid nodules should be followed up more aggressively than nodules detected at baseline screening.■

Walter JE, et al: Lancet Oncol 17:907-916, 2016.