Survival in pulmonary fibrosis combined with emphysema: likely defined by characteristics of specific patient subpopulations

Please see related letter http://www.fibrogenesis.com/content/4/1/16 webciteWe thank Cottin et al. for their interest in our work [1], and for sharing their engaging thoughts. They noted that our results appear to be in contrast with previous studies, and cite three references in support [2-4]. We agree that on the surface, there may be apparent disagreement with some previous results, but in-depth analysis does not suggest inconsistency between findings made by various groups of investigators.In the study by Cottin et al. [2], patients with combined pulmonary fibrosis and emphysema had a median survival of 6.1 years, a very similar survival time to our patients with advanced centrilobular emphysema combined with pulmonary fibrosis, who had a median survival of 6.2 years (75 months). Thus, these two reports are in full agreement on the duration of patient survival. However, contrasting the findings of both of these studies is another study of patients with idiopathic pulmonary fibrosis (IPF) and emphysema [3]. Of important note in this study, patients in the IPF and emphysema group had a median history of smoking of 5 pack-years, whereas in our study, patients with advanced emphysema and pulmonary fibrosis had a median 40 pack-year history of smoking. Because heavy cigarette smoking has been suggested to play a causative role in patients who develop emphysema combined with pulmonary fibrosis, it is not surprising that the outcomes differed between this study and our report. Further input on survival in patients with pulmonary fibrosis and emphysema comes from Antoniou et al. [4], who reported that 'findings were unchanged when the presence of emphysema ... was taken into account in survival analysis, with the presence of emphysema having no influence on survival.' However, this study focused not on patients with emphysema combined with fibrosis, but rather on comparing patients with IPF who were smokers versus those who were non-smokers. Smoking and emphysema are ce