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Correspondence |

The Relationship Between Emphysema on CT Scan and Lung Cancer FREE TO VIEW

Benjamin Smith, MD
Author and Funding Information

From the Department of Pulmonary Medicine, McGill University.

Correspondence to: Benjamin Smith, MD, Montreal Chest Institute, McGill University Health Centre, 3650 St-Urbain St, Montreal, QC, H2X 2P4, Canada; e-mail: benjamin.m.smith@mail.mcgill.ca


Financial/nonfinancial disclosures: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2011 American College of Chest Physicians


Chest. 2011;139(5):1259. doi:10.1378/chest.10-3229
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To the Editor:

I commend Maldonado and colleagues1 for their extended reanalysis of lung cancer screening data to explore the association between emphysema on CT scan and lung cancer in a recent issue of CHEST (December 2010). Attempts to validate previously published findings are all too rare.

The authors report the absence of a clear relationship between emphysema (quantitative or dichotomous) and the odds of lung cancer. As mentioned in the discussion, these findings differ from the more than threefold risk associated with emphysema found in two independent prospective cohort studies.2,3 Exploring why such different observations were made will help advance our understanding of the seemingly complex relationship between lung cancer, COPD, and emphysema on chest CT scans.

Maldonado et al1 acknowledge that Wilson et al3 observed an all-or-none effect, with even trace (<10%) or mild (10%-20%) emphysema increasing the risk of lung cancer. Yet their dichotomous analysis uses a threshold for emphysema at ≥15%. I would be interested to know the crude and adjusted impact of any emphysema (ie, >0%), as this was the threshold used by de Torres et al2 and Wilson et al.3 Indeed, from the data provided in Table 2 of the article by Maldonado et al1 with a threshold of ≥5%, the crude OR of lung cancer in the presence of emphysema is 1.7 (1.0-2.9). It may be that automated techniques or the threshold of −900 Hounsfield units generate too many false-positive diagnoses of minimal emphysema, a disease severity clinically important with respect to lung cancer risk.

Conversely, it is possible that the automated quantification technique used by Maldonado et al1 eliminated a potential observer bias in the studies of de Torres et al2 and Wilson et al.3 Lung cancer cases that were detected on the initial screening scan were presumably apparent to the CT scan readers (eg, masses, adenopathy) and may have influenced their assessment of emphysema. Such a bias could spuriously create a false association with lung cancer.

In summary, the work by Maldonado et al1 forces us to refine our understanding of the relationship between emphysema on CT scan and lung cancer and raises new research questions. Perhaps the application of their quantitative algorithm to the datasets of de Torres et al2 or Wilson et al3 or the manual grading of emphysema within their dataset would advance our understanding.

Maldonado F, Bartholmai BJ, Swensen SJ, Midthun DE, Decker PA, Jett JR. Are airflow obstruction and radiographic evidence of emphysema risk factors for lung cancer? A nested case-control study using quantitative emphysema analysis. Chest. 2010;1386:1295-1302. [CrossRef] [PubMed]
 
de Torres JP, Bastarrika G, Wisnivesky JP, et al. Assessing the relationship between lung cancer risk and emphysema detected on low-dose CT of the chest. Chest. 2007;1326:1932-1938. [CrossRef] [PubMed]
 
Wilson DO, Weissfeld JL, Balkan A, et al. Association of radiographic emphysema and airflow obstruction with lung cancer. Am J Respir Crit Care Med. 2008;1787:738-744. [CrossRef] [PubMed]
 

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Tables

References

Maldonado F, Bartholmai BJ, Swensen SJ, Midthun DE, Decker PA, Jett JR. Are airflow obstruction and radiographic evidence of emphysema risk factors for lung cancer? A nested case-control study using quantitative emphysema analysis. Chest. 2010;1386:1295-1302. [CrossRef] [PubMed]
 
de Torres JP, Bastarrika G, Wisnivesky JP, et al. Assessing the relationship between lung cancer risk and emphysema detected on low-dose CT of the chest. Chest. 2007;1326:1932-1938. [CrossRef] [PubMed]
 
Wilson DO, Weissfeld JL, Balkan A, et al. Association of radiographic emphysema and airflow obstruction with lung cancer. Am J Respir Crit Care Med. 2008;1787:738-744. [CrossRef] [PubMed]
 
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