The clinical significance of circulating tumor cells in non-metastatic colorectal cancer--a review.

BACKGROUND: Finding a clinical tool to improve the risk stratification and identifying those colorectal cancer patients with an increased risk of recurrence is of great importance. The presence of circulating tumor cells (CTC) in peripheral blood can be a strong marker of poor prognosis in patients with metastatic disease, but the prognostic role of CTC in non-metastatic colorectal cancer is less clear. The aim of this review is to examine the possible clinical significance of circulating tumor cells in non-metastatic colorectal cancer (TNM-stage I-III) with the primary focus on detection methods and prognosis.
METHODS: The PubMed and Cochrane database and reference lists of relevant articles were searched for scientific literature published in English from January 2000 to June 2010. We included studies with non-metastatic colorectal cancer (TNM-stage I-III) and CTC detected pre- and/or post-operatively in peripheral blood.
RESULTS: Nine studies qualified for further analyses. Detection rates of CTC in peripheral blood of patients with non-metastatic colorectal cancer varied from 4% to 57%. Seven studies applied RT-PCR and two studies used immunocytochemical methods. Seven studies found the presence of CTC to be a prognostic marker of poor disease-free survival.
CONCLUSION: The presence of CTC in peripheral blood is a potential marker of poor disease-free survival in patients with non-metastatic colorectal cancer. The low abundance of CTC in non-metastatic colorectal cancer requires very sensitive and specific detection methods. An international consensus on choice of detection method and markers, is warranted before incorporating CTC into risk stratification in the clinical setting.