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Background
Keywords
Findings
Authors
What is already known on this subject?
What does this study add?

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Background

The National Lung Screening Trial (NLST) demonstrated that low-dose computed tomography (LDCT) screening reduces lung cancer mortality in a high-risk U.S. population. A microsimulation model of LDCT screening was developed to estimate the impact of introducing population-based screening in Canada.

Methods

LDCT screening was simulated using the lung cancer module of the Cancer Risk Management Model (CRMM-LC), which generates large, representative samples of the Canadian population from which a cohort with characteristics similar to NLST participants was selected. Screening parameters were estimated for stage shift, LDCT sensitivity and specificity, lead time, and survival to fit to NLST incidence and mortality results. The estimation process was a step-wise directed search.

Results

Simulated mortality reduction from LDCT screening was 23% in the CRMM-LC, compared with 20% in the NLST. The difference in the number of lung cancer cases over six years varied by, at most, 2.3% in the screen arm. The difference in cumulative incidence at six years was less than 2% in both screen and control arms. The estimated percentage over-diagnosed was 24.8%, which was 6% higher than NLST results.

Interpretation

Simulated screening reproduces NLST results. The CRMM-LC can evaluate a variety of population-based screening strategies. Sensitivity analyses are recommended to provide a range of projections to reflect model uncertainty.

Keywords

LDCT, low-dose computed tomography, lung cancer screening, microsimulation, NLST, simulation

Findings

The National Lung Screening Trial (NLST) was conducted in the United States from August 2002 through April 2004 to determine if low-dose computed tomography (LDCT) screening could reduce lung cancer mortality. The NLST, which involved more than 53,000 participants, showed that three annual scans of a high-risk population resulted in a 20% reduction of lung cancer mortality after about six years of follow-up. Smaller European trials with somewhat different screening protocols and at-risk populations found either some evidence of lower mortality or no benefit. The U.S. Preventive Services Task Force rated the quality of these European trials as fair or less, but rated the NLST as a large, good-quality trial, and gave a grade B recommendation for annual LDCT screening of people aged 55 to 80 with a 30-pack-year smoking history who currently smoke or who quit within the past 15 years. However, the optimal "at-risk� population for screening is not known, nor is the optimal frequency or duration of screening. As well, the cost-effectiveness of LDCT and smoking cessation has been projected for a U.S. population, but not for Canada. [Full Text]

Authors

William M. Flanagan (bill.flanagan@statcan.gc.ca) is with the Health Analysis Division at Statistics Canada. William K. Evans and John R. Goffin are with McMaster University. Natalie R. Fitzgerald is with the Canadian Partnership Against Cancer. Anthony B. Miller is with the University of Toronto. Michael C. Wolfson is with the University of Ottawa.