Predictive factors for relapse in corticosteroid-treated patients with chronic eosinophilic pneumonia

Background: Chronic eosinophilic pneumonia (CEP) is an idiopathic disorder characterised by an abnormal and marked accumulation of eosinophils in the interstitium and alveolar spaces of the lungs. Systemic corticosteroid (CS) therapy leads to marked improvement. However, relapse is common in the clinical course, and the predictive factors for relapse of CEP are not well known. This study aimed to investigate predictive factors for relapse in CS-treated cases of CEP. Methods: We identified consecutive patients with CEP at our institution between 1999 and 2019. We retrospectively reviewed 36 CS-treated patients with CEP who underwent bronchoalveolar lavage (BAL) and high-resolution computed tomography (CT) at diagnosis. We examined relapse at least 1 year after the initiation of CS treatment. Statistical analysis included univariate and multivariate Cox proportional hazard regression analyses; P<0.05 was considered statistically significant. Results: The median (interquartile range) age at diagnosis was 59.5 years (47.8-70.0 years). This study included 13 men and 23 women. Twenty-five patients (69.4%) were never smokers and 15 (41.7%) had asthma. The peripheral blood eosinophil percentage was 35.0% (15.6-55.8%), and the BAL eosinophil percentage was 40.8% (10.7-68.5%). The median serum surfactant protein-D (SP-D) level was 135 ng/mL (82.2-176.7 ng/mL). High-resolution CT revealed centrilobular opacities in 23 patients (63.9%). Relapse of CEP was observed in 20 patients (55.6%). Higher serum SP-D levels and the presence of centrilobular opacities on high-resolution CT were significant predictors of relapse in multivariate Cox proportional hazard regression analysis (P=0.017 and P=0.028, respectively). Additionally, we devised a relapse prediction model for CS-treated CEP using two categorical parameters: the presence of centrilobular opacities and serum levels of SP-D (>135/<= 135 ng/mL). Based on these parameters, cases were scored 2, 1, or 0. Patients with a score of 2 experienced relapses earlier than those with scores of 1 and 0 (log-rank test; P=0.006, Conclusions: Centrilobular opacities on high-resolution CT and higher serum SP-D levels at diagnosis may be predictive factors for relapse in CS-treated patients with CEP.