Predictors of lung entrapment in malignant pleural effusion

Malignant pleural effusion (MPE) is a common complication in advanced stages of malignancy and is associated with poor prognosis. Non-expandable lung (NEL) often occurs and its presence influences the MPE approach. Our main objective was to assess risk factors for malignant NEL. Patients diagnosed with pathologically confirmed MPE between January 2012 and December 2018 in our institution were retrospectively analyzed. Demographic and clinical data of patients were reviewed and compared according to the presence or absence of NEL. A univariate and multivariate binary logistic regression analysis were used to determine predictors of the development of NEL. Of 365 patients included, 68 (18.6%) had NEL. After multivariate analysis, we found that loculated MPE (OR 8.63, 95%CI 4.30-17.33, p<0.001), complete hemithorax opacification (OR 2.81, 95%CI 1.17-6.76, p<0.021), lung cancer (OR 2.09, 95%CI 1.01-4.31, p=0.047) and higher effusion-serum LDH ratio (OR 1.09, 95%CI 1.00-1.17, p=0.039) were independent predictors of malignant NEL. There were no significant differences compared with expandable lung group regarding time from primary malignancy diagnosis to MPE diagnosis (3.0, IQR 0.0-75.8 vs 2.0, IQR 0.0-75.5 weeks, p=0.942) or MPE symptoms onset to MPE diagnosis (4.0, IQR 1.0-9.0 vs 3.0, IQR 1.0-9.0 weeks, p=0.497). Patients with NEL had a higher number of therapeutic pleural drainages (3.0, IQR 2.0-6.0 vs 2.0, IQR 1.0-3.0; p<0.001) and longer hospital stay (32.5, IQR 15.5-46.3 vs 21.0, IQR 11.0-36.0, p=0.007), measured in hospitalization days until the end of life, than patients with expandable lung. The rate of recurrence of pleural effusion was not significantly different between groups (p=0.291). Overall survival (OS) was 3.0 (95%CI, 2.3-3.7) months, regardless of lung expandability (p=0.923). Loculated MPE, complete hemithorax opacification, lung cancer and a higher effusion-serum LDH ratio were found to be independent predictors for NEL. These patients underwent thoracocenteses more frequently and had longer hospitalization days, although without significant impact in the OS.