We read with great interest the article by Dr. Wilson and colleagues entitled Association of Radiographic Emphysema and Airflow Obstruction with Lung Cancer. Regarding the relationship between emphysema and risk of lung cancer, we are delighted that this work reproduces the results previously published by our group, thus validating their significance. There are a few comments we would like to make about this important study.
First, although we acknowledge the differences in the study populations (age, smoking history and status, and clinical characterization), the higher prevalence of emphysema (47%) and chronic obstructive pulmonary disease (COPD) (47%) in comparison to our cohort is somewhat surprising. The higher prevalence of emphysema may be explained by the age (older) and smoking history (greater) of Wilson and coworkers' population.
Perhaps the higher prevalence of COPD is due to the fact that in their study, Wilson and coworkers performed spirometry without bronchodilator to diagnose and grade COPD. Lack of use of bronchodilators has elsewhere been associated with overdiagnosis of COPD in as many as 33% of individuals. In Wilson and coworkers' group, many individuals may not have COPD according to current defining criteria, and many othersmay have less severe COPD, both of which results could seriously influence the statistical analysis. We wonder whether a correct diagnosis of COPD by post-bronchodilator spirometry would also result in a negative association between airway obstruction and risk of lung cancer, as we found in our cohort.
Second, we encourage the authors to analyze the association between the pathologic characterization of the 99 lung cancers diagnosed in their cohort and the presence of emphysema. In our study, emphysema was associated more commonly with adenocarcinoma, and the tumors were located in the emphysematous areas in themajority of patients. Finally, we feel that a more detailed description of the protocol for the diagnosis of lung cancer in this screening trial is warranted.
We find that the drop in compliance to 25% by the third year is quite striking. In spite of these discrepancies, we believe that studies such as Wilson and coworkers' and the one published by our group underline the importance of the relationship between two of the most common and deadly diseases among smokers.
CITATION Am J Respir Crit Care Med. 2008 Dec 1;178(11):1187
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