Unenhanced low-dose CT scans that are used to screen heavy smokers for lung cancer also can identify a substantial percentage of cases of early-stage chronic obstructive pulmonary disease, according to a report in the October 26 issue of JAMA.
The results must still be validated in other cohorts, but "if CT scanning becomes widely adopted for lung cancer screening" it also could be used as a secondary test, outside of the primary and preferred method of screening with pulmonary function testing, to detect chronic obstructive pulmonary disease (COPD) early, wrote Dr. Onno M. Mets of the department of radiology at University Medical Center Utrecht (the Netherlands), and his associates.
"Early diagnosis is important because smoking cessation early in the COPD disease process slows disease progression and decreases morbidity and mortality," the authors noted.
Current CT technology "allows rapid in vivo evaluation of emphysematous parenchymal destruction and small airways dysfunction" by the assessment of air trapping, which "allows information on COPD-related changes to be obtained from CT studies performed for other reasons, such as lung cancer screening," they said.
"We hypothesized that CT-based lung cancer screening in heavy smokers could provide an opportunity to acquire information on the presence of COPD, without the need for obtaining pulmonary function testing," Dr. Mets and his associates wrote.
They assessed a subsample of 1,140 current and former heavy smokers participating in the Dutch Belgian Randomised Lung Cancer Screening Trial who underwent inspiratory and expiratory CT scanning, as well as pulmonary function testing, as part of the protocol for that trial.
"CT-based lung cancer screening in heavy smokers could provide an opportunity to acquire information on the presence of COPD."
All of the study participants were men aged 50-75 years (mean, 63). All had a smoking history of at least 16 cigarettes per day for 25 years or at least 11 cigarettes per day for 30 years – the equivalent of at least 16.5 pack-years.
Based on the results of pulmonary function testing, 437 men had COPD.
The CT scans accurately identified COPD in 274 of those men and gave false-positive results in 85. Thus, CT scans had a sensitivity of 63%, a specificity of 88%, a positive predictive value of 76%, and a negative predictive value of 79% in this cohort, Dr. Mets and his colleagues reported (JAMA 2011;306:1775-81).
The investigators detected COPD in 150 (54%) of 277 men with mild obstruction, 99 (73%) of 135 with moderate obstruction, and 25 of 25 with severe obstruction.
CT was more accurate in identifying COPD among men who were symptomatic than among those who were asymptomatic. This is probably because symptomatic men had more advanced disease, the investigators said.
Separate models for detecting COPD among symptomatic and asymptomatic men did not improve the results.
"Our study may add to the debate about whether and how to implement lung cancer screening for heavy smokers because we have shown that detection of COPD using low-dose screening CT scans may be feasible. Because smokers die not only from lung cancer but also from COPD and cardiovascular disease, the rationale for evaluating lung cancer screening CT scans for additional information may prove important," they wrote.
This study was supported by the Netherlands Organisation for Health Research and Development, Dutch Cancer Society Koningin Wilhelmina Fonds, Stichting Central Fund Reserves of Former Voluntary National Health Service Administration Insurances, Siemens Germany, Rotterdam Oncologic Thoracic Steering Committee, G. Ph. Verhagen Trust, Flemish League Against Cancer, Foundation Against Cancer, and the Erasmus Trust Fund. None of the authors had financial conflicts of interest.