Idiopathic Pulmonary Fibrosis and Lung Cancer. A Systematic Review and Meta-analysis

Rationale: The association between idiopathic pulmonary fibrosis (IPF) and lung cancer has been previously reported. However, there is the potential for significant confounding by age and smoking, and an accurate summary risk estimate has not been previously ascertained.Objectives: To determine the risk and burden of lung cancer in patients with IPF, accounting for known confounders.Methods: We conducted a comprehensive literature search of MEDLINE, EMBASE, and SCOPUS databases and used the Newcastle Ottawa criteria to assess study quality. We then assessed the quality of ascertainment of IPF cases based on modern consensus criteria. Data that relied on administrative claims or autopsies were excluded. We calculated summary risk estimates using a random effects model.Results: Twenty-five cohort studies were included in the final analysis. The estimated adjusted incidence rate ratio from two studies was 6.42 (95% confidence interval [CI], 3.21-9.62) and accounted for age, sex, and smoking. The summary incidence rate from 11 studies was 2.07 per 100 person-years (95% CI, 1.46-2.67), and the summary mortality rate was 1.06 per 100 person-years (95% CI, 0.62-1.51) obtained from three studies. The summary prevalence from 11 studies was 13.74% (95% CI, 10.17-17.30), and the proportion of deaths attributable to lung cancer was 10.20 (95% CI, 8.52-11.87) and was obtained from nine studies.Conclusions: IPF is an increased independent risk factor for lung cancer, even after accounting for smoking. Further well-designed studies using modern consensus criteria are needed to explore mechanisms of this association.