[Tumor markers for colorectal cancer]

CEA and CA19-9 are the two most common tumor markers for colorectal cancer that are currently utilized clinically. The positive rate of CEA is 40-60% and that of CA19-9 is 30-50%. Simultaneous use of the two markers is useful in evaluating the therapeutic effect and monitoring the recurrence of advanced colorectal cancer. Surgical specimens may also provide useful information for the appropriate treatment of patients. Using surgically resected lymph nodes, we examined micrometastasis to assess the spread of the cancer cells and the malignant potential of colorectal cancer. Immunohistochemical analysis using anti-cytokeratin antibody revealed no significant impact of micrometastasis on patient prognosis, while RT-PCR assay using CEA as a genetic marker suggested a positive value in predicting a rapid recurrence. Among various molecular markers, we found that CDC25B phosphatase was a powerful prognostic factor for colorectal cancer. Diagnosis of the existence and malignant potential of cancer cells, together with serum tumor marker levels, may help to construct a more useful system for the better treatment of colorectal cancer.