Objectives: We recently developed pleural lavage cytology for lung cancer patients without intraoperative signs of malignant pleuritis (Ann Surg Oncol, 4: 409, 1997). We analyzed recurrent patterns in pleural lavage cytology-positive lung cancer patients without intraoperative signs of malignant pleuritis based on semiquantitative evaluation of tumor cell clusters in pleural lavage solution.
Methods: Between December 1987 and December 1998, pleural lavage cytology-positive results after thoracotomy were obtained in 97 cases of lung cancer despite the lack of evidence of malignant pleuritis. Based on semiquantitative evaluation of the mean number of tumor cell clusters per slide in pleural lavage solution, patients were classified as Type I, in whom the mean number of clusters was < 1; Type II, in whom clusters numbered 1-10; and Type III, in whom clusters exceeded 10.
Results: Type I patients numbered 37, Type II 40, and Type III 20. By September 1999, pleural recurrence had occurred in 17 patients (18%)--2(5%) Type I, 4 (10%) Type II, and 11 (55%) Type III. The incidence of pleural recurrence was significantly higher for Type III patients, i.e., 5 of 11 Type III patients with pleural recurrence showed no sign of distant metastasis. In contrast, the main recurrent patterns in the other 2 groups were extrathoracic, nodal, and/or intrapulmonary.
Conclusions: The semiquantitative evaluation of tumor cell clusters in pleural lavage cytology-positive patients provided useful information on postoperative recurrence. Since Type III patients are at high-risk for pleural recurrence, postoperative therapy targeting local control should be conducted in such patients.