Prognostic significance of peritoneal lavage cytology in gastric cancer in Singapore.

BACKGROUND: Peritoneal lavage cytology has been included as part of the staging process in the 13th edition of the Japanese Classification of Gastric Cancer. However, this procedure has neither been studied nor established in our population. We aimed to evaluate its prognostic relevance among our patients with gastric cancer. METHODS: A total of 142 consecutive patients with gastric carcinoma were recruited prospectively. All had histologically proven gastric carcinomas and had undergone laparotomy and intraoperative peritoneal lavage for cytological examination at Singapore General Hospital. The fluid recovered was centrifuged and stained by the Papanicolau method. All patients were followed up with endpoints of cancer recurrence and mortality. RESULTS: There were 91 men and 51 women; 36 patients (25.4%) had positive peritoneal lavage. Patients with advanced macroscopic features, presence of vascular invasion, nodal involvement, advanced depth of tumor invasion and metastatic disease tended to have positive lavage, by univariate logistic regression analysis. Despite curative resections, patients with positive cytology had a more dismal disease-free survival (mean, 27 months vs 53 months; P < 0.0001 by log rank test) and higher recurrence rate (54.5% vs 19.3%; P = 0.007 by log rank test). There was also a trend towards earlier recurrences (median, 8 months vs 11 months; P = 0.37). By multivariate Cox regression stepwise analysis, advanced depth of tumor invasion and positive lavage cytology were found to be independent poor prognostic factors for disease-free survival. CONCLUSION: Positive peritoneal lavage cytology correlated well with advanced features of gastric cancer. It is an independent poor prognostic factor and the procedure should be routinely performed. Integration of lavage status into our current staging systems may serve as a guide for adjuvant therapeutic options to improve the survival of gastric cancer in our population.