Introduction: Given one third of the human population have been infected with tuberculosis, it is important to delineate the relationship between tuberculosis and lung cancer. This study explored whether contracting pulmonary tuberculosis is associated with an increased risk of developing lung cancers.
Methods: In a cohort of 716,872 insured subjects, free from cancers, aged 20 years and older, 4480 patients with newly diagnosed tuberculosis were identified from the universal insurance claims in 1998-2000 and tracked until 2007 with the remaining insured without tuberculosis. We compared the incidence of lung cancers between the two cohorts and measured the associated hazard of developing lung cancer.
Results: The incidence of lung cancers was approximately 11-fold higher in the cohort of patients with tuberculosis than nontuberculosis subjects (26.3 versus 2.41 per 10,000 person-years). Cox proportional hazard regression analysis showed a hazard ratio of 4.37 (95% confidence interval [CI]: 3.56-5.36) for the tuberculosis cohort after adjustment for the sociodemographic variables or 3.32 (95% CI: 2.70-4.09) after further adjustment for chronic obstructive pulmonary disease (COPD), smoking-related cancers (other than lung cancer), etc. The hazard ratio increased to 6.22 (95% CI: 4.87-7.94) with the combined effect with COPD or to 15.5 (95% CI: 2.17-110) with the combined effect with other smoking-related cancers.
Conclusions: This study provides a compelling evidence of increased lung cancer risk among individuals with tuberculosis. The risk may increase further with coexisting COPD or other smoking-related cancers.