All-cause mortality rate in patients with idiopathic pulmonary fibrosis. Implications for the design and execution of clinical trials

Am J Respir Crit Care Med. 2014 Apr 1;189(7):825-31. doi: 10.1164/rccm.201311-1951OC.


Rationale: FVC has emerged as a standard primary endpoint in clinical trials evaluating novel therapies for patients with idiopathic pulmonary fibrosis (IPF). However, it has recently been proposed that all-cause mortality or a composite comprised of all-cause mortality and all-cause nonelective hospitalization be adopted as the standard primary endpoint for IPF clinical trials.

Objectives: To conduct a comprehensive evaluation of mortality in three phase 3 clinical trials and evaluate the feasibility of mortality trials in patients with IPF.

Methods: The study population included 622 patients randomized to placebo in the CAPACITY studies evaluating pirfenidone (n = 347) or the INSPIRE study evaluating interferon-γ1b (n = 275). The Kaplan-Meier estimate of 2-year survival was fit to the exponential distribution and used to calculate sample size requirements for a mortality study with 90% power to detect a 25% reduction in all-cause mortality with a two-sided α of 0.05. Modeling analyses were used to assess the effects of selected variables on sample size and study design.

Measurements and main results: A total of 73 deaths occurred during the period of observation (mean duration of follow-up, 80.1 wk). The all-cause mortality rate was 6.6% at 1 year and 13.7% at 2 years. Based on the observed 2-year mortality rate, a total of 508 events would be required to detect a significant treatment benefit in a two-arm trial with 90% power to detect a 25% reduction in all-cause mortality. The estimated sample size for a trial enrolled over 3 years with a maximum follow-up period of 5 years is 2,582 patients.

Conclusions: The all-cause mortality rate is relatively low in patients with IPF with mild to moderate impairment in lung function. Accordingly, the necessary size, duration, and cost of all-cause mortality trials in this population are substantial and likely prohibitive.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Inflammatory Agents, Non-Steroidal / therapeutic use
  • Cause of Death
  • Clinical Trials, Phase III as Topic / methods*
  • Feasibility Studies
  • Female
  • Follow-Up Studies
  • Humans
  • Idiopathic Pulmonary Fibrosis / drug therapy
  • Idiopathic Pulmonary Fibrosis / mortality*
  • Interferon-gamma / therapeutic use
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Models, Statistical
  • Pyridones / therapeutic use
  • Randomized Controlled Trials as Topic / methods*
  • Recombinant Proteins / therapeutic use
  • Research Design*
  • Sample Size
  • Treatment Outcome


  • Anti-Inflammatory Agents, Non-Steroidal
  • Pyridones
  • Recombinant Proteins
  • interferon gamma-1b
  • Interferon-gamma
  • pirfenidone