Incidence and predictive factors of lung cancer in patients with idiopathic pulmonary fibrosis

Abstract

The incidence and risk factors of lung cancer in patients with idiopathic pulmonary fibrosis (IPF) have been poorly investigated. We conducted a retrospective study of 632 patients with IPF to assess the incidence and risk factors of lung cancer development. Seventy patients developed lung cancer over a median follow-up period of 3.8 years. The incidence density of lung cancer development was 25.2 cases per 1000 person-years. The most frequent type was squamous cell carcinoma (30%), the majority developed lung cancer in the peripheral lung (82.9%) and adjacent to usual interstitial pneumonia (75.7%). In a multivariate Cox regression hazard model, pack-years of smoking ≥35 and coexisting emphysema were associated with lung cancer development. The 1-, 3- and 5-year all-cause mortality rates after lung cancer diagnosis were 53.5%, 78.6% and 92.9%, respectively. The incidence density of lung cancer is high in IPF patients and occurs more frequently in patients with smoking history of pack-years of smoking ≥35 and with coexisting emphysema. The majority of lung cancers develop adjacent to usual interstitial pneumonia. Knowledge of these factors may help direct efforts for early detection of lung cancer and disease management.

FIGURE 1

Kaplan–Meier curve for the time until the development of lung cancer in patients with idiopathic pulmonary fibrosis. The 5- and 10-year cumulative lung cancer development rates were 12.2% and 23.3%, respectively. The incidence density of lung cancer development was 25.2 cases per 1000 person-years.

FIGURE 2

High-resolution computed tomography image showing a peripheral right lower lobe mass (arrow) and a usual interstitial pneumonia that exists around the mass to bottom of the lung.

FIGURE 3

Kaplan–Meier survival curves of all-cause mortality in patients with idiopathic pulmonary fibrosis (IPF). The 5- and 10-year mortality rates of all patients, patients who did not develop lung cancer and patients who developed lung cancer were 41.4% and 68.5%, 40.4% and 66.4%, and 46.9% and 76.7%, respectively. A log-rank test showed that the difference between survival curves of patients with or without lung cancer diagnosis was not significant (p=0.262).

FIGURE 4

Kaplan–Meier survival curves of all-cause mortality in patients with idiopathic pulmonary fibrosis after lung cancer development. The 1-, 3- and 5-year all-cause mortality rates after lung cancer diagnosis were 53.5%, 78.6% and 92.9%, respectively.