Prognostic impact of pleural effusion in EGFR-mutant non-small cell lung cancer patients without brain metastasis

Background In epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC), brain metastasis is known as a poor prognosis factor. However, prognostic factors in the patients without brain metastasis remain unclear. In this study, we aimed to clarify the differences between metastatic site and prognosis in common EGFR-mutant NSCLC patients without brain metastasis. Methods Chemotherapy-naive, advanced EGFR-mutant NSCLC patients without brain metastasis diagnosed between January 2010 and March 2016 were enrolled. We evaluated prognosis according to the presence or absence of bone metastases, liver metastasis, and pleural effusion. Results A total of 50 EGFR-mutant NSCLC patients without brain metastasis were enrolled. The median progression-free survival and overall survival were significantly shorter in patients with pleural effusion than in those patients without (progression-free survival 7.0 months, 95% confidence interval [CI] 3.7-13.0 vs. 13.0 months, 95% CI 9.1-21.7, hazard ratio [HR] 2.29, 95% CI 1.11-4.73, P = 0.020; overall survival 19.5 months, 95% CI 5.7-28.8 vs. 55.3 months, 95% CI 24.0-not evaluable, HR 3.00, 95% CI 1.35-6.68, P = 0.005). Pleural effusion was an independent factor of poor prognosis for progression-free survival (HR 3.44, 95% CI 1.50-7.88, P = 0.003) and overall survival (HR 2.34, 95% CI 1.00-5.44, P = 0.049). Conclusion Pleural effusion might be a poor prognosis factor for advanced EGFR-mutant NSCLC patients without brain metastasis treated with first-generation EGFR-tyrosine kinase inhibitors. Further precision medicine according to the metastatic site is required.