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

Abstract.

Aims: The aim of our study was to identify tumor cells in peritoneal lavage comparatively with immunocytochemistry (ICC) and half-nested reverse transcriptase-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 colorectum (n=49), stomach (n=17) or pancreas (n=9) and 13 patients with an abdominal aortic aneurysm (control group) the abdomen was irrigated with saline solution immediately after laparotomy. Cells were separated by Ficoll-density centrifugation and divided into 2 equal volumes for ICC and RT-PCR. For ICC cells were spun onto slides by cytospin centrifugation and stained with a monoclonal antibody (mab) against CEA using the APAAP method. For RT-PCR total RNA was extracted from the cells, transcribed into cDNA and amplified with CEA-specific primers. Lavages of 13 patients with an abdominal aortic aneurysm and blood samples of 6 healthy donors served as controls. Results: 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 by RT-PCR analysis. In the control group (n=13) no patient presented with tumor 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 significant correlations between detection rates and pT-, pN-, pM-categories as well 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 with poor prognosis. Moreover, these tumor cells are an independent prognostic factor and may have an influence on the development of peritoneal carcinomatosis. 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.