Molecular diagnostic detection of free cancer cells in the peritoneal cavity of patients with gastrointestinal and gynecologic malignancies.

Free cancer cells exfoliated from cancer-invaded serosa contribute to peritoneal dissemination, the most frequent pattern of recurrence in patients with gastric and ovarian cancers. This study was designed to evaluate the prognostic significance of free cancer cells in peritoneal washes detected using the reverse transcriptase-polymerase chain reaction (RT-PCR) and cytology. RT-PCR analysis with primers specific for the carcinoembryonic antigen (CEA) gene was found to be more sensitive than cytology for detection of free tumor cells in the peritoneal washes, collected at laparotomy from 199 gastric carcinoma patients, with higher detection rates for each of the T-categories in the TNM classification. Six patients with synchronous and 5 with recurrent peritoneal dissemination were found among 25 advanced cancer patients with positive PCR and negative cytology results. Positive PCR results were significantly associated with poor survival of curatively resected advanced gastric carcinoma patients (P < 0.001). A rapid method for detecting CEA mRNA using the LightCycler and the dsDNA binding dye SYBR green I was also developed. The results obtained using this technique were essentially the same as those obtained using the conventional RT-PCR method. Furthermore, RT-PCR analysis with primers specific for MUC1 epithelial mucin were performed on peritoneal washes from patients with ovarian cancer. Peritoneal washes from 21 of 25 ovarian carcinoma patients, including all 17 with positive cytology results, were positive for MUC1 mRNA, again indicating a higher sensitivity using this method than conventional cytology. Highly sensitive and rapid detection of free cancer cells in peritoneal washes, most reliably by RT-PCR, is a powerful technique to predict peritoneal dissemination in patients with gastric and ovarian cancers.