[Utility of dopa decarboxylase as a novel marker for the detection of peritoneal micro-metastases of gastric cancer with realtime RT-PCR].

We have examined the utility of DDC as a novel marker for the detection of peritoneal micrometastases of gastric cancer. DDC mRNA in the peritoneal wash from 114 gastric cancer patients was quantified for a comparison of carcinoembryonic antigen (CEA) mRNA by means of real-time RT-PCR with a fluorescently labeled probe to predict peritoneal recurrence. The cut-off value was set at the upper limit of the quantitative value for non-cancer patients, and those above this cut-off value constituted the micrometastasis (MM+) group. Thirteen of 15 cases with peritoneal dissemination were MM+DDC (87% sensitivity), and one of 48 t1 cases was MM+ (98% specificity). DDC levels in peritoneal washes from patients with synchronous peritoneal metastases were more than 50 times higher than in those from patients without metastasis (p<0.01). For 15 cases of peritoneal dissemination (seven cases were cytologically positive), DDC was positive in 13 cases (87% sensitivity), but CEA failed to detect micrometastases in four cases (73% sensitivity), indicating that DDC is in some cases superior to CEA for the detection of peritoneal micrometastases of gastric cancer in terms of sensitivity as well as specificity, especially for poorly differentiated adenocarcinomas. Combination of CEA and DDC improved the accuracy of diagnosis up to 93%. These results suggest that DDC is potentially a novel marker for peritoneal dissemination of gastric cancer and that quantitative RT-PCR of DDC is reliable and efficient for the selection of patients for adjuvant intraperitoneal chemotherapy to prevent peritoneal recurrence.