Long-term prognostic value of conventional peritoneal cytology after curative resection for colorectal carcinoma

This study was undertaken to evaluate the long-term prognostic significance of conventional peritoneal cytology in patients with advanced colorectal carcinoma after curative resection.

A review was performed of 189 patients who underwent curative resection for pT3/T4 carcinoma of the colon and upper/middle rectum between March 1987 and December 1991. Patient outcomes were reviewed retrospectively. Peritoneal cytology was performed before manipulation of the tumor. Intraoperatively, 50 ml of saline were instilled and 20 ml were reaspirated for cytology. In all patients, Papanicolaou and Giemsa stainings were performed to detect intraperitoneal free tumor cells.

The median follow-up was 103 months. Malignant cells were identified in peritoneal washings from 11 patients (5.8%). Of the 11 patients with positive cytology, six (54.5%) developed recurrence and peritoneal recurrence was observed in four (36.4%). In contrast, of the 178 patients with negative cytology, 46 (25.8%) developed recurrence and peritoneal recurrence was observed in four (2.2%). The peritoneal recurrence rate was significantly increased (P = 0.0004) in the patients with positive cytology. The cancer-specific 10-year survival rates for the patients with positive and negative cytology were 45.5 and 80.3%, respectively (P = 0.0051). Multivariate analysis (Cox proportional hazard model) revealed that peritoneal cytology (positive: P = 0.0256) and lymph node metastasis (pN2: P = 0.0004) were independent predictors of cancer-specific survival.

Conventional peritoneal cytology serves as a new prognostic marker after curative resection in patients with advanced colorectal carcinoma. It appears to be a useful diagnostic procedure for predicting recurrence, especially peritoneal recurrence.