Incidence and prognostic value of positive peritoneal cytology in colorectal cancer

Purpose: This study was conducted to investigate the incidence of free cancer cells in the peritoneal washings of patients who had undergone surgery for colorectal cancer and to evaluate its influence as a prognostic factor of the disease. Methods: From 1990 to 1996, intraoperative washing cytology was performed in 110 patients who underwent surgery for colorectal cancer. All patients had curative resections. Immediately after the abdomen was opened and before exploration and mobilization of the tumor, 100 ml of saline was injected over the tumor site. Washings were then aspirated and taken for cytologic examination. Results: Twenty-two (20 percent) of 110 patients examined were found to have positive cytology for intraperitoneal free malignant cells. The site of tumor in the colon or rectum, tumor size, nodal status, degree of differentiation, mucinous characteristics, and vascular or neural invasion were found not to affect the incidence of free cancer cells. Conversely, tumor penetration was found to affect the incidence of positive cytology. The degree of association among the stages of tumor penetration was indicated by the contingency coefficient, which was 0.42. Patients with positive cytology had a significantly higher rate of local recurrence and peritoneal carcinomatosis (22.8 vs. 8 percent, P=0.05) than patients with negative cytology. Mortality rate was not found to be related to the presence of free cancer cells. Conclusion: Cytologic examination of peritoneal lavage at the time of surgery could be a useful prognostic indicator for local and peritoneal recurrence rate. However, it was not found to be a predictor of survival.