Impact of coexisting idiopathic pulmonary fibrosis on prognosis in patients with lung cancer: a nationwide cohort study

Idiopathic pulmonary fibrosis (IPF) is associated with lung cancer, but its clinical impact in patients with lung cancer remains unclear. We evaluated the prevalence of coexisting IPF and its association with mortality and healthcare utilization among patients with newly diagnosed lung cancer. Using the Korean National Health Insurance Service Health Screening Cohort, we identified 10,123 incident lung cancer cases between 2002 and 2019. Propensity score overlap weighting was applied to balance baseline characteristics, and treatment-adjusted models were used to examine whether associations persisted after accounting for treatment differences. IPF prevalence at lung cancer diagnosis was 0.593%. In treatment-adjusted models, IPF was associated with higher all-cause mortality (hazard ratio [HR] 1.72, 95% confidence interval [CI] 1.34–2.21) and lung cancer–related mortality (HR 1.78, 95% CI 1.38–2.31). IPF was also associated with increased respiratory-related hospitalization (HR 1.83), emergency room visits (HR 1.65), intensive care unit admissions (HR 4.41), and admission frequency (incidence rate ratio [IRR] 2.88), as well as fewer days alive and out of hospital. These findings suggest that coexisting IPF is associated with substantially increased mortality and respiratory healthcare burden in lung cancer.