Researchers have leveraged quantitative CT to identify two types of structural changes in the lungs of patients with chronic obstructive pulmonary disease (COPD) associated with frequent exacerbations, according to a study published online July 25 in Radiology. The findings may help identify patients for targeted research and therapy development for individual phenotypes.
“COPD is an extremely common problem that is frustrating to physicians,” said the study’s lead researcher MeiLan K. Han, MD, an assistant professor of medicine at the University of Michigan Health System in Ann Arbor. “For a long time, we have had a one-size-fits-all approach to treating COPD patients.”
Han and colleagues pointed out that acute exacerbations of COPD present a hefty burden and are associated with impaired quality of life, more rapid decline in lung function and higher mortality. In addition, treatment of exacerbations accounted for a majority of the nearly $50 billion in COPD spending in the U.S. in 2010, according to the National Heart, Lung and Blood Institute (NHLBI).
A method to predict patients at high risk for acute exacerbation could help healthcare providers target preventive therapy, and improve on spirometry, the current COPD staging method, surmised Han and colleagues.
“Spirometry is inadequate as the sole parameter for assessing risk of exacerbations,” Han said. “Two COPD patients may be identical in terms of lung function yet behave very differently. For instance, there are subsets of patients with severely reduced lung function who do not experience frequent exacerbations.”
The researchers analyzed data from the COPDGene Study, an ongoing multicenter NHLBI-sponsored study, designed to identify genetic factors associated with COPD. In the study, patients between the ages of 45 and 80 with a history of cigarette smoking undergo spirometry and whole-lung volumetric CT exams.
The study group included the first 2,500 patients enrolled in the COPDGene Study who met criteria for COPD. The researchers studied whether there was an association between a patient’s bronchial wall thickness and degree of air sac destruction on CT with frequency of exacerbations as reported on self-administered questionnaires.
The analysis revealed that many patients had a mixture of structural changes related to their COPD and identified two CT phenotypes of subjects who experienced increased exacerbations independent of spirometric measures of lung function: an emphysema-predominant group and an airway-predominant group.
“Our findings support the utility of radiologic phenotyping with use of whole-lung volumetric high-spatial-resolution CT. … These radiologically defined subgroups of patients who experience more frequent exacerbations have clinical distinct symptoms and physiologic and comorbidity profiles that ultimately may lead to a better understanding of the heterogeneity inherent to COPD,” wrote Han.
“Radiologic characterization of COPD patients has prognostic value in the selection of more homogeneous subgroups for clinical trials and possibly for identifying patients at risk of frequent exacerbations for targeted medical therapies,” Han and colleagues concluded.