Surgical intervention for non-small-cell lung cancer with minimal malignant pleural effusion.

PURPOSE: We assessed the clinical significance of minimal malignant pleural effusion (MPE) using liquid-based cytology (LBC) and immunocytochemistry and reviewed the postoperative outcomes of patients with non-small-cell lung cancer (NSCLC). METHODS: We reviewed 240 patients with cM0 NSCLC who underwent lobectomy. Carcinoembryonic antigen (CEA) immunocytochemistry was performed with LBC to aid in the diagnosis of minimal MPE. We assessed the efficacy of this diagnostic method, relevant clinical factors, and postoperative outcomes. RESULTS: LBC showed positive results in two patients and suspicious results in 21. Of the 21 patients, immunocytochemistry showed minimal MPE in 10 (47.6%); therefore, a total of 12 patients (5%) showed minimal MPE. Minimal MPE is associated with an older age, increased consolidation tumor ratio, and adenocarcinoma histology. The 12 patients with minimal MPE had a 3-year overall survival rate of 90%. Postoperative recurrence was observed in seven patients (58.3%), four of whom were treated with epidermal growth factor receptor-tyrosine kinase inhibitors or immune checkpoint inhibitors, while three are still undergoing treatment, with a survival of 2.2, 2.5 and 5.5 years. CONCLUSIONS: CEA immunocytochemistry offers high sensitivity for the diagnosis of minimal MPE. Surgical intervention may be considered for select patients with NSCLC showing minimal MPE.