Prognostic significance of free gastrointestinal tumor cells in peritoneallavage detected by immunocytochemistry and polymerase chain reaction

Aims: The aim of our study was to identify tumor cells in peritoneal lavage comparatively with immunocytochemistry (ICC) and half-nested reverse trans criptase-polymerase chain reaction (RT PCR) using carcinoembryonic antigen (CEA) as marker and to evaluate their prognostic significance. Patients and methods: In 75 patients who underwent surgery for a carcinoma of the color ectum (n=49), stomach (n=17) or pancreas (n=9) and 13 patients with an abdo minal aortic aneurysm (control group) the abdomen was irrigated with saline solution immediately after laparotomy. Cells were separated by Ficoll-dens ity centrifugation and divided into 2 equal volumes for ICC and RT PCR. For ICC cells were spun onto slides by cytospin centrifugation and stained wit h a monoclonal antibody (mab) against CEA using the APAAP method. For RT PC R total RNA was extracted from the cells, transcribed into cDNA and amplifi ed with CEA-specific primers. Lavages of 13 patients with an abdominal aort ic aneurysm and blood samples of 6 healthy donors served as controls. Resul ts: Immunostained tumor cells were found in peritoneal lavage in 23% (17/75 ) of all patients, whereas 63% (47/75) of patients gave a positive result b y RT PCR analysis. In the control group (n=13) no patient presented with tu mor cells in ICC, however 5 of 13 (38%) showed amplified CEA-mRNA by RT-PCR , and so did one of six blood samples. Using ICC technique, we found signif icant correlations between detection rates and pT, pN-, pM-categories as we ll as tumor stage. On the contrary, by RT PCR significant correlations were observed only between pT- and pM-categories and detection rates. Detection of tumor cells in peritoneal lavage with both techniques was associated wi th poor prognosis. Moreover, these tumor cells are an independent prognosti c factor and may have an influence on the development of peritoneal carcino matosis. Conclusion: ICC is a useful method for detection of tumor cells in peritoneal lavage. In contrast, half-nested RT-PCR cannot be recommended, as the detection rates are unproportionally high, obviously as a result of CEA-mRNA expression in nontumor cells.