Quantity of smoking tied to reduced survival in patients with progressive fibrosing ILD

Heavy smoking, based on pack-years, in adults with progressive fibrosing interstitial lung disease was associated with increased risk for mortality, according to research published in Respiratory Medicine.

“[Pack-years] was an independent predictor of mortality after adjusting for age, sex, lung function and ILD diagnosis,” Mark G. J. P. Platenburg, MD, PhD candidate in the department of pulmonology at the ILD Center of Excellence at St. Antonius Hospital in Nieuwegein, the Netherlands, and colleagues wrote. “This is supported by our finding that the survival of heavy smokers, defined as [20 pack-years or more], compared with mild to moderate, is significantly decreased.”

The retrospective cohort study included 377 patients (mean age, 67.2 years; 65% men; mean number of pack-years, 16.8) who met the INBUILD trial criteria for progressive fibrosing ILD. Researchers collected data on smoking pack-years and compared median transplant-free survival between heavy smokers with 20 or more pack-years and mild to moderate smokers with 0.1 to 19.9 pack-years.

Independent predictors of mortality in patients with progressive fibrosing ILD included age, percent predicted FVC and DLCOc, diagnosis of idiopathic pulmonary fibrosis and pirfenidone or mycophenolate mofetil treatment.

Researchers reported significant hazard ratios for pack-years in both unadjusted (HR = 1.014; 95% CI, 1.006-1.022; P < .001) and adjusted (HR = 1.011; 95% CI, 1.002-1.021; P = .022) models. Risk for mortality was 11% higher for those with 10 pack-years, 22% higher for those with 20 pack-years and 44% higher for those with 40 pack-years.

Median transplant-free survival was 3.3 years for ever-smokers compared with 4.8 years for never-smokers (P = .031). When the researchers examined subgroups of patients categorized as heavy and mild to moderate smokers, median transplant-free survival was 3 years among heavy smokers and 3.8 years for mild to moderate smokers (P = .035). The researchers did not report a difference in survival between different ILD subtypes.

“[Our] data shows that each additional pack-year is accumulating risk on mortality and stresses the importance of smoking cessation. This is an important message that clinicians could convey to their ILD patients, but also to patients at risk for ILD, [such as] those with systemic sclerosis, rheumatoid arthritis and relatives of ILD patients,” the researchers wrote.

Emphysema was present more often among mild to moderate smokers compared with never-smokers (P = .016). More patients with emphysema were heavy smokers compared with never-smokers or mild to moderate smokers (68 vs. 5 and 21, respectively; P < .001 for both).

“Taken together, our data indicates that efforts to reduce pack years in those with, and at-risk for, [progressive fibrosing]-ILD may translate into a survival benefit and should have higher priority in clinical practice,” the researchers wrote.