Asthma as a Risk Factor for Lung Cancer

Rationale Chronic inflammation has been found as precursor for cancer. Asthma produces inflammatory reactions of the lung tissue that can last for years. Nevertheless, literature shows conflicting data with weak associations and controversial results. Purpose Evaluate if asthma is a risk factor for lung cancer. Methods Two meta analysis of epidemiologic literature were carried out, one with 17 case-control studies and one with 16 cohort studies carefully selected from peer reviewed journals. These studies included the calculation of the global odds ratio and relative risk respectively. The heterogeneity among studies, publication bias and the sensitivity of the global estimates were evaluated. Meta analysis graphical and statistical procedures were used. Results After a careful selection of high quality cohort studies, it was found that people with asthma have 50% more risk of developing lung cancer than those without asthma (RR = 1.5, 95% CI 1.1, 1.9). Regarding the results for case-control studies, those with lung cancer (cases) had 40% larger odds to have had asthma than controls without lung cancer (OR = 1.4, 95% CI 1.2, 1.5). Conclusions The two meta analysis included in this investigation, show that asthma, in fact, is a risk factor for lung cancer in spite of the lack and controversial results of some published research. Asthma patients are at a higher risk to develop lung cancer and should be screened for early diagnosis and treatment more often than the rest of the population. More studies are necessary to define the pathophysiology of this relationship.