National Lung Screening Trial Analysis Supports Risk-based Targeting of Smokers for Low-dose CT Screening
The National Lung Screening Trial (NLST) showed that screening with low-dose computed tomography (CT) resulted in a 20% reduction in lung cancer mortality compared with chest radiography in participants aged 55 to 74 years with a minimum of 30 pack-years of smoking and no more than 15 years since quitting. In a study reported in The New England Journal of Medicine, Stephanie A. Kovalchik, PhD, of the National Cancer Institute, and colleagues analyzed the number of lung cancer deaths prevented and false-positive rates with low-dose CT screening in the NLST according to a validated model for predicting 5-year risk of lung cancer death. They found that increasing risk was associated with a greater number of CT screening–prevented lung cancer deaths and a lower number of false-positive results per death prevented.
Study Details
The model for predicting 5-year risk of lung cancer death included age, body mass index, family history of lung cancer, pack-years of smoking, years since smoking cessation, and emphysema diagnosis. The model for competing causes of death added sex and race to these risk factors and excluded family history of lung cancer. A total of 26,604 participants who underwent low-dose CT screening and 26,554 participants who underwent chest radiography were categorized into risk quintiles, with 5-year risk ranging from 0.15% to 0.55% in the lowest risk quintile (quintile 1) to > 2.00% in the highest quintile (quintile 5).
Outcomes
The number of lung cancer deaths per 10,000 person-years that were prevented in the CT screening group compared with the radiography group increased according to risk quintile: 0.2 in quintile 1, 3.5 in quintile 2, 5.1 in quintile 3, 11.0 in quintile 4, and 12.0 in quintile 5 (P = .01 for trend).
The proportion of subjects with false-positive results on CT screening decreased with increasing risk (97% in quintile 1 vs 88% in quintile 5, P < .001 for trend), although the total number of subjects with false-positive results increased with increased risk (1,648 in quintile 1 vs 2,146 in quintile 5, P < .001 for trend). The number of subjects with false-positive results per CT screening–prevented death significantly decreased with increasing risk: 1,648 in quintile 1, 181 in quintile 2, 147 in quintile 3, 64 in quintile 4, and 65 in quintile 5 (P < .001 for trend).
The 60% of participants at highest risk for lung cancer death (quintiles 3–5) accounted for 88% of the CT screening–prevented lung cancer deaths and for 64% of participants with false-positive results. The 20% of participants in quintile 1 accounted for only 1% of prevented lung cancer deaths.
The investigators concluded: “Screening with low-dose CT prevented the greatest number of deaths from lung cancer among participants who were at highest risk and prevented very few deaths among those at lowest risk. These findings provide empirical support for risk-based targeting of smokers for such screening.”
The study was funded by the National Cancer Institute.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
