Does the presence of circulating tumor cells in the venous drainage of curative colorectal cancer resections determine prognosis? A meta-analysis

Background: Hepatic metastasis can occur following curative colorectal cancer surgery despite favorable prognostic indicators, raising the question of whether detecting circulating tumor cells in the venous drainage of colorectal cancers at resection using reverse-transcriptase polymerase chain reaction would help determine prognosis. This study compares lymph node positivity, hepatic metastasis rates, and disease-free survival in circulating tumor positive versus negative patients. Methods: A Medline, Embase, Ovid, and Cochrane database search was conducted on all studies between 1999 and 2006 reporting the outcomes of interest. Meta-analysis was performed in line with recommendations from the Cochrane Collaboration and the Quality of Reporting of Meta-Analyses guidelines. Results: Nine studies reporting on 646 subjects published between 1998 and 2006 matched the selection criteria and were suitable for inclusion in this meta-analysis. There was a significantly higher incidence of circulating tumor cells (50%) in lymph node positive compared with negative groups (21%) [odds ratio (OR) = 3.83, confidence interval (CI) = 2.46-5.94], and a significantly increased hepatic metastases rate (21%) in circulating tumor cells positive compared with in negative patients (8%, OR = 6.38; CI = 2.67-15.25. Disease-free survival was significantly higher in the circulating tumor cell negative versus positive groups at 1 year [hazard ratio (HR) = 0.04, CI = 0-0.46], 2 years (HR = 0.05, CI = 0.01-0.31), and 3 years (HR = 0.08, CI = 0.02-0.34) post resection. Conclusion: This study highlights the potential importance of free cancer cell detection in the venous drainage of colorectal cancers as a prognostic indicator and a mode of staging colorectal cancers.