SEROLOGICAL EVIDENCE OF AN ASSOCIATION BETWEEN CHLAMYDIA-PNEUMONIAE INFECTION AND LUNG-CANCER

Epidemiological evidence suggests that airway obstruction is an indepe ndent risk factor for lung cancer and that this cannot be explained by active or passive smoking alone. Chlamydia pneumoniae infection has b een associated with chronic bronchitis and its exacerbates. Our aim wa s to evaluate the association between chronic C. pneumoniae infection and risk of lung cancer among male smokers. Smoking males with lung ca ncer (n = 230) and their age- and locality-matched controls were selec ted among participants of the Alpha-Tocopherol. Beta-Carotene Cancer P revention Study. The presence of C. pneumoniae infection was assessed by analyzing specific antibodies and immune complexes in 2 serum sampl es collected with a 3-year interval before the lung cancer diagnosis. The diagnosis of chronic infection was based on stable levels of posit ive specific IgA antibody (titer greater than or equal to 16) and immu ne complex (titer greater than or equal to 4). Relative risks were est imated by odds ratios (OR) adjusted for age, locality and smoking hist ory by a conditional logistic regression model. Markers suggesting chr onic C. pneumoniae infection were present in 52% of cases and 45% of c ontrols and hence were positively associated with the incidence of lun g cancer (OR 1.6; 95% confidence interval [CI] 1.0-2.3). The incidence was especially increased in men younger than 60 years (OR 2.9; 95% CI 1.5-5.4) but not in the older age group (OR 0.9; 95% CI 0.5-1.6). Bef ore concluding that C. pneumoniae infection is a new independent risk factor for lung cancer, corroboration from other studies with larger n umber of cases and longer follow-up is needed. (C) 1997 Wiley-Liss, In c,.