A Prospective Study on the Significance of Peritoneal Washing Cytology as a Diagnostic Modality in Colorectal Cancer

ABSTRACT

PURPOSE: Free intraperitoneal cancer cells exfoliated from a tumor are considered to be responsible for peritoneal dissemination. Therefore, microscopic evaluation of cells washed from the peritoneal cavity during surgery for various intraabdominal malignancies has been used to detect subclinical intraperitoneal metastases from these tumors. The purposes of this study were to detect intraperitoneal free cancer cells at the time of surgery by using peritoneal washing cytology in colorectal cancer and to evaluate their diagnostic significance. METHODS: During the 29-month period from January 2000 through May 2002, 149 randomly selected patients with primary colorectal cancer without evidence of gross peritoneal metastasis underwent peritoneal washing cytologic analysis before surgical manipulation of the tumor. Peritoneal washing cytology was compared with the pre-existing prognostic factors. RESULTS: Positive peritoneal washing for free cancer cells was found in 19 of 149 patients (12.8%). This positivity was significantly correlated with histologic grade (P=0.002), serosal invasion (P=0.025), lymph node metastasis (P=0.034), Astler-Coller classification (P=0.008), recurrence (P<0.001), and 5-year survival (P<0.001). Cancer-specific survival was significantly associated with histologic grade (P=0.025), peritoneal washing cytology (P<0.001), lymph node metastasis (P<0.001), recurrence (P<0.001), and stage (P= 0.010) in the multivariate analysis. CONCLUSIONS: The presence of free cancer cells was predictive of survival and was an independent prognostic factor. This information may be useful in stratifying patients with colorectal cancer for therapeutic trials, such as intraperitoneal chemotherapy.