Pleural lavage cytology in non-small cell lung cancer: Lessons from 1000 consecutive resections

Objective: Intraoperative pleural lavage cytology for lung cancer has not been widely accepted. The prognostic significance of this procedure has yet to be intensively analyzed because the reports published thus far have involved small patient populations. We therefore performed a large prospective trial of pleural lavage cytology to elucidate its importance. Methods: Cytologic status of pleural lavage fluid before any manipulation of the lung was examined in 1000 consecutive patients with non-small cell lung cancer but no pleural effusion who underwent tumor resection. Results: Forty-five (4.5%) of 1000 patients had positive cytologic findings. Positive cytologic findings were observed more frequently in patients with adenocarcinoma, advanced stage, higher involvement of lymph nodes, pleural involvement of the tumor, lymphatic permeation, vascular invasion, high level of serum carcinoembryonic antigen, and male sex. The survival rate for 5 years was 28% in patients with positive findings and 67% in patients with negative findings (P<.0001). Among 587 patients with stage I disease, 13 (2.2%) had positive findings, and their 5-year survival was 43%, which was significantly poor compared with that of patients with negative findings (81%, P=.0009). Multivariable analysis demonstrated that pleural lavage cytology was an independent prognostic determinant (P=.0290). Regarding the recurrence pattern in patients with positive findings, distant metastases (19/45 [42.2%]) were observed more frequently rather than local recurrences (19/45 [22.2%]). Conclusions: Cytologic status of pleural lavage fluid immediately after thoracotomy, an independent significant prognostic factor, constitutes valuable information to detect patients at a high risk of recurrence. Therefore cytology should be performed at the time of curative resection for non-small cell lung cancer.