medwireNews: Findings from an extended follow-up of the National Lung Screening Trial (NLST) maintain that low-dose computed tomography (LDCT) screening significantly reduces risk for lung cancer death versus chest radiography (CXR) screening among high-risk current and former smokers.
Participants screened using LDCT had an 8% reduction in the risk for lung cancer death compared with those screened using CXR, with a respective 1147 versus 1236 lung cancer deaths occurring over a median 12.3 years of follow-up.
This translates into a number needed to screen (NNS) to prevent one lung cancer death of 303, report Paul Pinsky (National Cancer Institute, Bethesda, Maryland, USA) and colleagues in the Journal of Thoracic Oncology.
These results build on the initial findings from the NLST, in which an NNS of around 320 was recorded after a median follow-up of 6.5 years. According to the researchers: “The stability of this difference [in NNS] over time indicates that LDCT screening did not just delay lung cancer death by a few years, but prevented it, or at least delayed it for more than a decade.”
In the US-based NLST, men and women aged 55–74 years with at least 30 pack–years of cigarette smoking, and who continued to smoke or had quit within the last 15 years, were randomly assigned to receive three annual screens with either LDCT or single-view CXR. The 53,452 participants were actively followed up for 5 years from the end of the initial study in 2004, and then passively through linkages with state cancer registries and the National Death Index.
And although earlier results from the NLST reported a modest but statistically significant increase in the incidence of lung cancer in the LDCT arm (rate ratio [RR]=1.13), possibly indicating overdiagnosis, the current report, with a median follow-up of 11.3 years for incidence, found similar numbers of lung cancer cases in the LDCT and CXR arms, at a respective 1701 and 1681 (RR=1.01).
“This indicates that so-called ‘catch-up’ likely occurred in the CXR arm, where the counterparts of those cancers diagnosed early in the LDCT arm were eventually diagnosed in the CXR arm,” suggest the researchers.
They conclude: “With further follow-up of NLST subjects, the originally reported reduction in lung cancer deaths in the LDCT versus CXR arm was sustained; in contrast, the originally reported increase in lung cancer incidence was no longer observed.”
By Catherine Booth
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