Heterogeneity in survival among adult cystic fibrosis patients with low lung function in the United States

Background Lung transplantation (LTx) is frequently considered for patients with cystic fibrosis (CF) when FEV1 reaches <30%. This study estimated transplant-free survival for patients with CF and FEV1 <30% and identified predictors of transplant-free survival. Methods We conducted a retrospective cohort study using the Cystic Fibrosis Foundation Patient Registry, 1/1/2003-12/31/2013. Adult patients (≥18 years) with FEV1 <30% prior to LTx were included. We performed Kaplan-Meier survival estimates censored at LTx. Multivariable Cox proportional hazard regression identified adjusted predictors of survival. Results There were 3,340 patients with FEV1 <30%. Death without LTx occurred in 1,250 (37.4%); 945 (28.3%) underwent LTx; 924 (27.7%) remained alive without LTx at the end of the follow-up period; 221 (6.6%) were lost to follow-up. Median transplant-free survival after FEV1 <30% was 6.6 years (95% CI 5.9-7.0). Adjusted predictors of mortality included (HR, 95% CI): supplemental oxygen use (2.1, 1.7-2.6), B. cepacia infection (1.8, 1.3-2.6), BMI ≤18 (1.6, 1.3-1.9), female sex (1.6, 1.2-2.0), CF-related diabetes on insulin (1.4, 1.2-1.8), and ≥1 exacerbations per year (1.7, 1.3-2.2; vs. 0 exacerbations). Conclusions Median survival is over 6.5 years for CF patients with FEV1 <30%, exceeding prior survival estimates. There is substantial heterogeneity in survival, with some CF patients dying soon after reaching this lung function threshold and others living for many years. For this reason, we conclude that FEV1 <30% remains an important marker of disease severity for patients with CF, but we suggest FEV1 value alone need not always trigger LTx evaluation.