Peritoneal dissemination is one of the most common modes of gastric cancer recurrence even after curative resection. Cytological examination of peritoneal lavage fluid is useful for detection of free cancer cells in the peritoneal cavity. However, some patients with negative cytological findings have peritoneal metastases of their gastric cancer. The purpose of the present study was to investigate the incidence and clinical significance of metastases harbored in the peritoneal cavity of patients with gastric carcinoma. Peritoneal lavage fluid was collected from the left subphrenic or Douglas cavities of 136 gastric cancer patients without macroscopic peritoneal metastases and 31 patients with benign disease. Peritoneal lavage fluid was examined by both conventional cytological examination (Papanicolaou and Giemsa staining), and carcinoembryonic antigen (CEA)-specific reverse transcription-polymerase chain reaction (RT-PCR). Among 136 gastric cancer patients, 5 patients (3.6%) were positive for free cancer cells by cytological examination and 30 (22.1%) were positive by RT-PCR. A difference in positivity between the left subphrenic and Douglas cavity was found in 18 patients by RT-PCR. The frequency of RT-PCR results increased according to lymph node metastases, lymphatic invasion, depth of tumor invasion and stage grouping. The incidence of peritoneal recurrence was significantly higher in patients with positivity than those with negativity by RT-PCR (p<0.0001). Among cytologically negative patients, survival was significantly shorter in patients with positive than in those with negative CEA-mRNA expression (p<0.0001). The technique of RT-PCR was more sensitive than cytological examination in the detection of cancer cells and prediction of peritoneal recurrence. Adjuvant therapy may be advisable for the gastric cancer patients with positive findings of peritoneal lavage by RT-PCR.

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