CT screening highly sensitive, specific for lung cancer detection

By Shreeya Nanda, Senior medwireNews Reporter

Low-dose computed tomography (CT) screening for lung cancer has high specificity and high sensitivity, with just a small number of interval cancers, finds an interim analysis of the NELSON trial.

In this prespecified analysis of the NELSON study, Nanda Horeweg, from Erasmus University Medical Center in Rotterdam, the Netherlands, and colleagues assessed the “performance of the screening test to detect interval cancers, and provide insights into the incidence, histopathology, and causes for failed detection of these cancers.”

A total of 15,822 individuals aged between 50 and 75 years and considered at high risk of lung cancer as a result of prior smoking habits (smoking at least 15 cigarettes per day for more than 25 years or at least 10 cigarettes per day for more than 30 years) were enrolled in the NELSON trial. The participants were randomly assigned to undergo CT screening at years 1, 3 and 5.5 after baselineor to receive no screening.

The analysis included data from the 7155 participants who attended at least one screening. During a median follow-up of 8.16 years, 187 (3%) patients were diagnosed with 196 cancers detected by CT screening.

Additionally, using data from the Dutch cancer registry, the researchers found that 34 (<1%) patients were diagnosed with 35 interval cancers, of which 19 patients were diagnosed in the year following CT and 15 in the second year after screening.

When the data from the first 3 years of screening were combined with those from 2 years of follow-up, the sensitivity and specificity of CT screening for lung cancer detection were found to be 84.6% and 98.6%, respectively. Moreover, CT screening had a positive predictive value of 40.4% and a negative predictive value of 99.8%.

Retrospective assessment of the last available CT records showed that in 12 of the 34 individuals with interval cancers, the lesions had not been visible on the scan, whereas in the remaining 22 patients, the lung cancer was missed, mainly owing to detection or interpretation errors.

Interval cancers were significantly more likely to be diagnosed at stage III or IV compared with screen-detected lesions (83 vs 22%), were more likely to be small-cell carcinomas (20 vs 4%) and less likely to be adenocarcinomas (26 vs 52%), Horeweg et al report in The Lancet Oncology.

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