Three hundred forty-two patients with lung cancer and 99 patients with nonneoplastic lung diseases (control group) underwent intraoperative pleural lavage with 300 ml physiologic saline solution before (lavage I) and after resection (lavage II).

Studies of the lavage fluid in all control patients were negative, that is, there were no false positive findings. Tumor cells were found in lavage I in 132 patients (38.6%) and also in lavage II in 99 of them. In stage I (pT1 N0, pT2 N0) lung cancer, tumor cell detection was possible in 47 patients (28.6%). The 4-year survival of patients with resected non-small-cell lung cancer was 24% (95% confidence interval, 16% to 32%) if lavage I results were positive and 52% (95% confidence interval, 45% to 59%) if lavage I results were negative (all stages, p = 0.007). For patients with stage I disease (n = 164) the 4-year survival was 35% (95% confidence interval, 18% to 52%) if lavage I results were positive (n = 47), and 69% (95% confidence interval, 60% to 78%) if lavage I results were negative (n = 117) (p = 0.037). On multivariate analysis the positive cytologic result in intraoperative pleural lavage was an additional prognostic factor for our patients. To prove how the tumor cells enter the pleural cavity, we performed tissue cultures of tumor-free parenchyma in 23 cases of lung cancer. Tumor cell detection by histology and immunohistology was possible in 16 cases (69.6%). Detection of tumor cells in pleural lavage fluid before resection proves that tumor cells have spread into the pleural cavity.

The positive result in pleural lavage seems to be a prognostic predictor for patients with lung cancer.