Prognostic Value of Peritoneal Cytology and the Combination of Peritoneal Cytology and Peritoneal Dissemination in Colorectal Cancer

PURPOSE:The value of positive peritoneal cytology in colorectal cancer has been controversial. In this study, we aimed to clarify the prognostic significance of peritoneal cytology and the impact of the combination of peritoneal dissemination and peritoneal cytology on the prognostic evaluation of colorectal cancer. METHODS:From January 1997 to December 2005, intraoperative peritoneal cytology was performed on 410 patients who had at least serosal invasion. RESULTS:Thirty-one patients (7.6%) had positive peritoneal cytology. Patients with negative cytology showed a significantly better survival rate at five years than those with positive cytology (negative cytology, 68.0%; positive cytology, 20.6%; P < 0.0001). Multivariate analysis revealed that peritoneal cytology is one of the significant prognostic factors. Sixty percent of patients with positive cytology and 30.4% of patients with negative cytology recurred (P = 0.08). Regarding the recurrence site, patients with positive cytology showed a significantly higher recurrence rate of peritoneal dissemination than those with negative cytology (P = 0.0038). Some patients with positive cytology but without evident peritoneal dissemination achieved long-term survival. Additionally, some patients with macroscopic peritoneal dissemination and negative peritoneal cytology also achieved long-term survival. But for those patients with both positive cytology and evident macroscopic peritoneal dissemination, the five-year survival rate was zero. CONCLUSIONS:Patients with negative peritoneal cytology had a significantly better five-year survival rate than those with positive peritoneal cytology. In some cases in which either peritoneal cytology or peritoneal dissemination was negative, long-term survival could be achieved.