Lung cancer in patients with chronic obstructive pulmonary disease-- incidence and predicting factors

Little is known about the clinical factors associated with the development of lung cancer in patients with chronic obstructive pulmonary disease (COPD), although airway obstruction and emphysema have been identified as possible risk factors.

To explore incidence, histologic type, and factors associated with development of lung cancer diagnosis in a cohort of outpatients with COPD attending a pulmonary clinic.

A cohort of 2,507 patients without initial clinical or radiologic evidence of lung cancer was followed a median of 60 months(30–90). At baseline, anthropometrics, smoking history, lung function,and body composition were recorded. Time to diagnosis and histologic type of lung cancer was then registered. Cox analysis was used to explore factors associated with lung cancer diagnosis.

A total of 215 of the 2,507 patients with COPD developed lung cancer (incidence density of 16.7 cases per 1,000 person-years). The most frequent type was squamous cell carcinoma (44%). Lung cancer incidence was lower in patients with worse severity of airflow obstruction. Global Initiative for Chronic Obstructive Lung Disease Stages I and II, older age, lower body mass index,and lung diffusion capacity of carbon monoxide less than 80%were associated with lung cancer diagnosis.

Incidence density of lung cancer is high in outpatients with COPD and occurs more frequently in older patients with milder airflow obstruction (Global Initiative for Chronic Obstructive Lung Disease Stages I and II) and lower body mass index. A lung diffusion capacity of carbon monoxide less than 80% is associated with cancer diagnosis. Squamous cell carcinoma is the most frequent histologic type. Knowledge of these factors may help direct efforts for early detection of lung cancer and disease management.