AIM:To investigate whether gene methylation in the peritoneal fluid (PF) predicts peritoneal recurrence in gastric cancer patients.METHODS: The gene methylation of CHFR (checkpoint with forkhead and ring finger domains), p16, RUNX3 (runt-related transcription factor 3), E-cadherin, hMLH1 (mutL homolog 1), ABCG2 (ATP-binding cassette, sub-family G, member 2) and BNIP3 (BCL2/adenovirus E1B 19 kDa interacting protein 3) were analyzed in 80 specimens of PF by quantitative methylation-specific polymerase chain reaction (PCR). Eighty patients were divided into 3 groups; Group A (n=35):the depth of cancer invasion was less than the muscularis propria; Group B (n=31): the depth of cancer invasion was beyond the muscularis propria. Both group A and B were diagnosed as no cancer cells in peritoneal cytology and histology; Group C (n=14): disseminated nodule was histologically diagnosed or cancer cells were cytologically defi ned in the peritoneal cavity.RESULTS: The positive rates of methylation in CHFR, E-cadherin and BNIP3 were significantly different among the 3 groups and increased in order of group A, B and C (0%,0% and 21% in CHFR, P<0.05; 20%, 45% and 50% in E-cadherin, P<0.05;26%,35% and 71% in BNIP3, P<0.05). In addition, the multigene methylation rate among CHFR, E-cadherin and BNIP3 was correlated with group A, B and C (9%,19% and 57%, P<0.001). Moreover, the prognosis was analyzed in group B, excluding 3 patients who underwent a non-curative resection. Two of the 5 patients with multigene methylation showed peritoneal recurrence after surgery, while those without or with a single gene methylation did not experience recurrence (P<0.05).CONCLUSION: This study suggested that gene methylation in the PF could detect occult neoplastic cells in the peritoneum and might be a risk factor for peritoneal metastasis.
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