Background: Peritoneal recurrence is the most common type of recurrence in gastric cancer. Although cytological examination of peritoneal lavage fluid has been used to predict peritoneal spread, peritoneal recurrences often occur even in patients with negative cytology. Our previous retrospective study suggested that reverse transcriptase-polymerase chain reaction (RT-PCR) using peritoneal lavage fluid may be useful for predicting peritoneal recurrence in patients with negative cytology. This prospective study was conducted to validate the clinical impact of this RT-PCR method. Methods: From July 2009 to June 2012, a total of 118 cT2-4 gastric cancer patients underwent surgery. Since 14 patients were ineligible because they had incurable factors, the remaining 104 eligible patients were evaluated for carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20) messenger RNA (mRNA) using RT-PCR. If either CEA or CK20 mRNA was detected by RT-PCR, the patient was defined as PCR-positive as in our previous study. The association between recurrence-free survival (RFS) and background factors was analyzed using Cox proportional hazards models. Results: Of 104 patients, 16 (15.4 %) were positive for either CEA or CK20. PCR-positive patients had significantly worse RFS than PCR-negative patients (log-rank p = 0.007). Regarding the pattern of recurrence, 4 of 16 (25 %) PCR-positive patients and 2 of 88 (2 %) PCR-negative patients had peritoneal recurrence (p < 0.001), but there were no significant differences in recurrence at other sites. Cox multivariate analysis indicated only PCR-positivity as a significant predictor of poor RFS (p = 0.029). Conclusion: This prospective study demonstrated that CEA and CK20 PCR results could predict peritoneal recurrence after curative surgery.
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