CT screening for lung cancer: Importance of emphysema for never smokers and smokers
Introduction
The number of people who have a CT scan of the chest continues to increase in the United States and throughout the world for many indications, including CT screening for lung cancer. In 2009, it was estimated that in the US alone, almost 10 million CT scans of the chest were performed for lung and cardiac indications [1]. It is estimated that over 50% of these people had at least one noncalcified nodule (NCN) identified in the lung parenchyma, raising the possible diagnosis of lung cancer [2]. Beyond the identification of NCNs on CT scans, emphysema has been identified as an important risk factor for lung cancer which appears to be independent of the presence of airflow obstruction as measured by pulmonary function tests [3], [4], [5], [6].
In light of the high lung cancer fatality rate, the management of findings on CT is of great concern. Different management strategies have been developed with a goal of diagnosing a possible cancer as early as possible while minimizing unnecessary diagnostic tests, invasive procedures, and surgery. These strategies have focused mainly on high-risk smokers in the context of CT screening studies [7], [8], [9], [10], [11]. The Fleischner Society Guidelines also addressed the recommended workup for NCNs in low-risk individuals, including never smokers [12]. These management strategies, however, do not use the information on findings provided by the CT scan other than the presence of NCNs.
In this report we address the prevalence of lung cancer according to the presence of emphysema as identified in the CT scan in both high and low-risk people as defined by their smoking history and age.
Section snippets
Methods
Participants (n = 62,124) enrolled in a program of CT screening for lung cancer in the International Early Lung Cancer Action Program (I-ELCAP) in 2000–2013 [13]. At the time of enrollment, all were 40–90 years of age (median age of 60) and asymptomatic for lung cancer. Consent for the research was obtained from all participants according to HIPAA-compliant protocols that were approved by the IRBs of the participating institutions.
Results
The characteristics of the 62,124 participants at the time of the baseline CT scan are given in Table 1, separately for current, former and never smokers. On average, former smokers were older than current and never smokers (62 vs. 57 vs. 56 years of age, P < 0.0001). The median pack-years of smoking were 35 pack-years (IQR: 23–49) for current smokers and 30 (IQR: 19–47) for former smokers. For former smokers, the median years of quitting prior to enrollment was 15 years (IQR: 6–24). Gender and
Discussion
Our study demonstrated an increase in the prevalence of lung cancer among those who also had CT evidence of emphysema, thereby demonstrating the importance of identifying emphysema when interpreting a CT scan of the chest. While this increased risk of lung cancer has been previously reported for smokers [3], [4], [5], [6], this is the first such report for never smokers. In never smokers, when emphysema was identified as seen in 1.6% of never smokers in our report, that person had the same
Conflict of interest statement
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Dr. Yankelevitz is a named inventor on a number of patents and patent applications relating to the evaluation of diseases of the chest including measurement of nodules. Some of these, which are owned by Cornell Research Foundation (CRF), are non-exclusively licensed to General Electric. As an inventor of these patents, Dr. Yankelevitz is entitled to a share of any compensation which CRF may receive from its commercialization of these patents. Dr. Yankelevitz also serves on the scientific
Acknowledgements
This report has been funded in part by the Flight Attendant Medical Research Institute. The sponsor had no involvement in any study design, data collection, data analysis and interpretation and manuscript writing.
The screenings in the I-ELCAP pooled database has been supported in part by National Institutes of Health R01-CA-63393l and R01-CA-78905; Department of Energy DE-FG02-96SF21260; The City of New York, Department of Health and Mental Hygiene; New York State Office of Science, Technology
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See Appendix A.