Quantitative Detection of Disseminated Free Cancer Cells in Peritoneal Washes With Real-Time Reverse Transcriptase–Polymerase Chain Reaction

OBJECTIVE: To evaluate the feasibility of real-time reverse transcriptase-polymerase chain reaction (RT-PCR) detection of free cancer cells in the peritoneal washes as a prognostic indicator for patients with gastric carcinoma. SUMMARY BACKGROUND DATA: Peritoneal lavage cytology (CY) is an excellent prognostic determinant but lacks sensitivity. This can be improved by using RT-PCR to quantitate carcinoembryonic antigen (CEA) mRNA in peritoneal washes. METHODS: Peritoneal washes were obtained from 189 patients with gastric carcinoma during laparotomy. CEA mRNA levels and CEA/GAPDH mRNA ratios were quantified using a real-time PCR system with fluorescent hybridization probes. Receiver-operating characteristic plots were used to determine which of these parameters should be used as a marker for the intraperitoneal cancer cells. The prognostic significance of its positivity was then evaluated by Kaplan-Meier curves, and its value as an independent prognostic factor was evaluated by multivariate analysis. RESULTS: The sensitivity and specificity of real-time RT-PCR with an optimal cutoff value were 80% and 94%; those for conventional cytology were 56% and 91%. The survival of 16 patients who were CY-PCR+ was poor and approached that of 35 CY+ patients. Recurrence as peritoneal carcinomatosis was frequent among PCR+ patients but rare for their PCR- counterparts. PCR+ was a significant independent prognostic factor, along with the presence of node metastasis and serosal invasion, but CY+ was not. CONCLUSIONS: Quantitative RT-PCR of peritoneal washes can replace cytologic examination as a tool for the sensitive evaluation of the risk of intraperitoneal recurrence in patients with gastric carcinoma.