Examination of cancer cells exposed to gastric serosa by serosal stamp cytology plus RT-PCR is useful for the identification of gastric cancer patients at high risk of peritoneal recurrence.

BACKGROUND: We sought to clarify the clinical value of the examination of cancer cells exposed to gastric serosa by our novel method of serosal stamp cytology and a real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis.

METHOD: A total of 70 patients who underwent gastrectomy were enrolled. Stamp cytology specimens were obtained by stamping the gastric serosa at the primary gastric tumor lesion, followed by Papanicolaou's staining. Samples obtained by brushing the serosa at the primary gastric tumor were analyzed by our RT-PCR of carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20).

RESULTS: Among the 70 patients, 11 patients were diagnosed as stamp cytology-positive. Eight and five patients were found to be CEA-positive and CK20-positive, respectively. Since 21 of the 70 patients were either stamp cytology-positive or RT-PCR analysis-positive, these 21 patients were considered to be positive for cancer cells exposed to serosa of primary gastric tumor. The 3-year recurrence-free survival rate of the patients with a single positive result by our method (41.7%) was significantly (log rank p = 0.0002) worse than that of the patients with both negative results (81.0%). Our method showed 58.8% sensitivity and 79.2% specificity. A multivariate analysis revealed that a stamp cytology and/or RT-PCR result was an independent prognostic factor for recurrence.

CONCLUSION: The examination of cancer cells exposed to gastric serosa by our serosal stamp cytology and RT-PCR system will be useful for the identification of patients at high risk for peritoneal recurrence after curative surgery for gastric cancer.