Background: The significance of detection of circulating cancer cells in blood during surgery in patients with colorectal cancer (CRC) remains controversial. Experimental study revealed that the cancer cells injected from the vein disappeared completely until 7 days. The aim of this study was to clarify that the detection of circulating cancer cells in blood taken later than 7 days after curative surgery may be a prognostic factor.
Methods: Two hundred consecutive patients with CRC who underwent potentially curative surgery were the subjects. Peripheral blood was collected between 7 and 10 days after resection. Cancer cells were detected using reverse transcriptase-polymerase chain reaction targeting carcinoembryonic antigen (CEA) messenger RNA (mRNA). The median follow-up period was 52 months (range: 34-69 months).
Results: The overall positive incidence of CEA mRNA was 22%. Detection of CEA mRNA was not significantly related to conventional clinicopathological findings. Recurrence has been confirmed in 55 patients (28%). The recurrence rate was significantly higher in patients with rectal cancer, deep penetration, lymph node metastasis, preoperative chemoradiotherapy and positive CEA mRNA. The CEA mRNA positive patients showed significantly poorer disease free survival (DFS) and overall survival (OS) than the negative patients (DFS, P = 0.007; OS, P = 0.04). Multivariate analysis revealed that the positive expression of CEA mRNA (P < 0.01) as well as the tumor location and TNM stage classification was identified as the significant risk factors for recurrence.
Conclusions: Detection of CEA mRNA expressing cells in peripheral blood 7 days after curative surgery is a novel independent factor predicting recurrence in patients with CRC.