Combined pulmonary fibrosis emphysema: Role of cigarette smoking and pulmonary hypertension in a rural cohort

Abstract

Background: Disease heterogeneity in idiopathic pulmonary fibrosis (IPF) often complicates the systematic study of disease, management of patients and clinical investigations. Objective: To describe combined pulmonary fibrosis emphysema (CPFE) phenotype in a rural Appalachian IPF cohort with the highest smoking rates in the United States. Methods: CPFE patients (n = 60) in a developed IPF cohort (n = 153) were characterized. Groups (CPFE vs IPF without emphysema) were categorized based on the predominant HRCT patterns of UIP (n = 109). Demographics, clinical variables, and treatment details were recorded. Kaplan–Meier survival and multivariate logistic regression analysis were performed. Results: The prevalence of CPFE in our IPF cohort was 45% (n = 49). The CPFE group was younger (73.9 vs 78.2), had a more extensive smoking history (93.9% vs 53.3%) with greater mean smoking pack years (49.09 vs 15.39) and had lower percentage predicted DLCO on presentation (38.35 vs 51.09) compared to IPF without emphysema group. Both groups shared equivalent higher burden of comorbidities, including pulmonary hypertension (PH) (46.9% vs 33.3%). One-fifth of patients were prescribed antifibrotics and only a subset (5%) of patients underwent lung transplantation. There was a non-significant trend towards reduced survival in CPFE (p = 0.076). Smoking status and DLCO predicted CPFE in our cohort. Body mass index (BMI), PH, and pirfenidone use were significant predictors of mortality. Conclusion: CPFE was highly prevalent in our rural IPF cohort. In contrast to previous studies, CPFE group was older and had higher female (approx. 30%) occurrence. A greater exposure to cigarette smoke and reduced DLCO at diagnosis predicted CPFE. Lower BMI and PH predicted higher mortality whereas use of pirfenidone improved survival in our cohort. This study highlights a complex interaction of cigarette smoking, advanced fibrosis of UIP, PH and potential utility of antifibrotic agents in CPFE phenotype. Substantial burden of comorbidities, older age, and the limited utilization of advanced therapeutics in the cohort emphasize the challenges faced by rural Appalachian patients.