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A recent analysis compared low-dose computed tomography with chest radiography in a sample of patients eligible for the National Lung Screening Trial.

Compared with chest radiography, low-dose computed tomography (CT) improved mortality outcomes in a nationally representative sample of patients with lung cancer, according to new findings published in JAMA Network Open.

The National Lung Screening Trial (NLST) showed superior lung cancer-specific and all-cause mortality with low-dose CT scans, inspiring new recommendations from the US Preventive Services Task Force (USPSTF), wrote lead author Sarah E. Robertson, PhD, affiliated with the Harvard T.H. Chan School of Public Health, and coauthors. However, the USPSTF’s updated guidance cautions that results from the trial may not apply to the patient populations seen in practice.

“Several studies have found that NLST participants are younger, have fewer comorbidities, and are more educated compared with populations seen in practice who would be candidates for CT screening. Therefore, we need to extend inferences about the comparative effectiveness of screening by low-dose CT vs chest radiography from the NLST to target populations that are representative of populations seen in practice,” Dr. Robertson and colleagues wrote.

A Nationally Representative Target Population

To better understand if the trial’s findings remained consistent for a nationally representative target population of US adults, Dr. Robertson and colleagues conducted a comparative effectiveness study. They used transportability analysis to reweight data from the NLST, combining baseline covariate, treatment, and outcome data from the trial with covariate data from the 2010 National Health Interview Survey (NHIS).

The NLST enrolled patients from 33 sites in the United States between August 2002 and April 2004. Follow-up was conducted through 2009. Patients were eligible if they were 55-74 years of age and were current or former smokers with at least 30 pack-years of smoking. Former smokers must have quit within 15 years prior to study enrollment, the authors reported.

Dr. Robertson’s analysis involved 51,274 participants from the NLST and 685 participants from the NHIS. After survey-weighting the data, the study team reported that the participants represented a target population of approximately 5.7 million people.

The primary outcomes were lung cancer-specific death and all-cause death. Researchers noted that the median follow-up was 5.5 (5.2-5.9) years for lung cancer-specific mortality and 6.5 (6.1-6.9) years for all-cause mortality.

Low-Dose CT Scans Versus Chest Radiography

Regarding lung cancer-specific mortality, researchers estimated a relative rate reduction of 18% (95% CI, 1%-33%) in the target population versus 21% (95% CI, 9% to 32%) in the NLST.

Compared to chest radiography, low-dose CT yielded an estimated absolute rate reduction of 71 deaths per 100,000 person-years (95% CI, 4-138 deaths per 100 000 person-years) in the target population and 67 deaths per 100 000 person-years (95% CI, 27 to 106 deaths per 100 000 person-years) in the NLST.

Meanwhile, the estimated relative rate reductions in all-cause mortality were comparable between the target population and the NLST, at 6% (95% CI, −2%-12%) and 7% (95% CI, 0%-12%), respectively.

The analysis was subject to several limitations.

“Our analyses estimate the effectiveness of screening policies under adherence similar to that observed in the NLST. Yet, adherence to screening in the NLST was approximately 90%, whereas adherence to screening in community settings is lower,” Dr. Robertson and colleagues wrote.

In addition, the researchers adjusted for several comorbidities but could not adjust for competing events when estimating lung cancer-specific mortality. The team also could not adjust for the evolution in screening strategies and other therapeutic advancements since the NLST was completed, so investigators said their findings underestimate the comparative effectiveness of newer CT screening.

Nevertheless, Dr. Robertson and colleagues concluded their “results suggest that low-dose CT screening resulted in improved outcomes compared with chest radiography in a nationally representative population [of] NLST-eligible individuals, indicating that the trial findings are transportable to this target population.”