Importance of chronic airway obstruction as a risk factor for lung cancer

Although chronic airway obstruction (CAO) and lung cancer are cardinal sequelae to cigarette smoking, it has not been conclusively settled whether CAO may increase the risk predisposing to the development of lung cancer. To address this issue, various pulmonary-function tests were conducted for lung cancer patients without endobronchial lesions (LC group, n=79). The LC group was divided into three subgroups based on the pathological findings, i.e., squamous cell carcinoma (n=29), adenocarcinoma (n=36), and small cell carcinoma (n= 14). Subjects, suffering from extra-thoracic malignancies but not lung cancer, in whom age distribution, smoking exposure and body mass index (BMI) were matched to those of the LC group were enrolled as the control (ETM group: n=94). All the patients selected were male and their ECOG performance status was not impaired. % predicted values of VC, FEV ₁, PEF, V ₅₀, and V ₂₅ calculated from the equation constructed from the data obtained for nonsmoking healthy Japanese subjects were used as indicators expressing the extent of CAO. While %VC values were comparable between any groups, %FEV ₁, %PEF, %V ₅₀ and %V ₂₅ in the squamous cell carcinoma group deteriorated more severely than those in the ETM control group. %FEV ₁, %PEF, %V ₅₀ and %V ₂₅ values in the adenocarcinoma group were significantly reduced as compared to those in the ETM group. None of the pulmonary function parameters of the small cell carcinoma group differed from those in the ETM group. These findings may suggest that chronic airway obstruction plays a role as an additional risk factor for developing non-small cell lung cancer but not small-cell lung cancer.