Detection of tumor cells in the portal and peripheral blood of patients with colorectal carcinoma using competitive reverse transcriptase‐polymerase chain reaction

BACKGROUND In spite of many reports, it remains unclear whether the presence of tumor cells in circulating blood flow predicts a poor prognosis. METHODS Competitive seminested reverse transcriptase‐polymerase chain reaction (RT‐PCR), a technique for the quantitative detection of tumor cells, was applied to detect the presence of tumor cells in portal and peripheral blood samples from 121 patients with colorectal carcinoma and to clarify their clinical significance. This technique can detect one carcinoembryonic antigen (CEA) mRNA‐expressing tumor cell in 1 × 105 normal lymphocytes. RESULTS Six of 33 healthy volunteers (18%) demonstrated a positive reaction to this technique. CEA mRNA expression was detected in the portal blood in 51% of patients and in the peripheral blood in 42% of patients. The results from the two blood samples were consistent in 91% of patients. The positive expression rates for portal blood in patients with T1 tumors and those with TNM Stage I disease were 38% and 45%, respectively. The positive rate was significantly higher in patients with colon carcinoma and those with Stage III or IV disease. CEA mRNA expression, quantitatively measured (× 10−8/β‐actin), was 22.9 ± 35.1 in the portal blood and 19.9 ± 40.0 in the peripheral blood, with no statistically significant difference. A significant positive correlation was noted between portal and peripheral CEA mRNA expression levels according to Speaman correlation analysis (correlation coefficient = 0.78; P < 0.01). Multivariate analysis revealed that the positive rate and level of CEA mRNA expression in the portal and peripheral blood did not appear to be influenced by the established prognostic factors. CONCLUSIONS The presence of circulating tumor cells might be of less value as a prognostic factor because they also can be detected in patients with early‐stage colorectal carcinoma and appeared to be independent of the conventional prognostic factors. Cancer 2001;92:1251–58. © 2001 American Cancer Society. Colorectal carcinoma cells can be detected in patients with early‐stage disease. The majority of the tumor cells from the primary site are not arrested by the liver, but enter into the systemic circulation.