Association of Chronic Chlamydia pneumoniae Infection and the Risk of Lung Cancer

Study Objectives: Chlamydia pneumoniae, a respiratory tract patho­gen, have tendency to cause chronic infections and suspected to play a role in the development of lung cancer. In this study, we aimed to evaluate the association between chronic 0. pneumoniae infection and the risk of lung cancer.

Patients and Methods: Sixty newly diagnosed lung cancer patients and 35 healthy controls were included in this case-control study. IgA and IgG antibodies to C. pneumoniae were measured with commercial kits.

Results: The prevalence of C. pneu­moniae specific IgA and IgG seropositivity were significantly higher in lung cancer patients compared to healthy controls. IgA seropositivity was detected in 45% of lung cancer patients and 14.3% of control cas­es (p=0.002). IgG seropositivity was detected in 70% of lung cancer patients and 28.6% of control cases (p=0.0001). C. pneumoniae spe­cific IgA and IgG antibodies increased the risk of lung cancer 4.6 and 5.3 fold respectively, independent from age, sex, and smoking history. C. pneumoniae specific IgA antibody was significantly more common in non small-cell lung cancer patients.

Conclusions: C. pneumoniae specific IgA and IgG antibodies were independently associated with risk of lung cancer. This finding suggested the contribution of chronic C. pneumoniae infection to malignant transformation.