Rapid quantitative detection of carcinoembryonic antigen-expressing free tumor cells in the peritoneal cavity of gastric-cancer patients with real-time RT-PCR on the lightcycler

Int J Cancer. 2000 Sep 20;89(5):411-7. doi: 10.1002/1097-0215(20000920)89:5<411::aid-ijc3>3.0.co;2-5.


Detection of free cancer cells in the peritoneal cavity by RT-PCR using carcinoembryonic antigen (CEA) as a target gene is a more sensitive predictor of peritoneal dissemination than conventional cytology in gastric-cancer patients. Difficulties with this method are the lack of quantitative assessment of free cancer cells and the length of time before completion. To overcome these problems, we have established a rapid and quantitative detection method using a novel real-time fluorescence PCR system (LightCycler). Using this device with hybridization probes as fluorophores, we detected CEA mRNA in peritoneal washes during surgery (within 3 hr) without any post-PCR procedure. This method could reproducibly quantitate 10 to 10(6) CEA-expressing colon carcinoma cells per 10(7) peripheral blood leukocytes, a comparable sensitivity to conventional RT-PCR with a wide dynamic range. Analysis of peritoneal washes from 109 gastric-cancer patients with this assay revealed relative values of CEA transcripts that correlated well with the depth of tumor invasion (p < 0.01). Average values of CEA transcript in peritoneal washes in patients with cytology (-)/RT-PCR(-), cytology (-)/RT-PCR(+) and cytology (+)/RT-PCR(+) results were 0.64, 1,525 and 6,715, respectively. Moreover, CEA transcripts in peritoneal washes in patients with synchronous peritoneal metastasis were more than 50-fold higher than in those without metastasis. These results suggest a positive correlation between CEA mRNA levels in peritoneal washes and prognosis. We conclude that real-time RT-PCR with hybridization probes is a sensitive, quantitative, specific and rapid method to detect free cancer cells in peritoneal washes. This clinically relevant system is a powerful technique to evaluate the risk of peritoneal recurrence in patients with gastric cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinoembryonic Antigen / analysis*
  • Carcinoembryonic Antigen / genetics
  • Glyceraldehyde-3-Phosphate Dehydrogenases / genetics
  • Humans
  • Neoplasm Staging
  • Peritoneal Cavity / pathology*
  • RNA, Messenger / analysis
  • Reverse Transcriptase Polymerase Chain Reaction*
  • Stomach Neoplasms / pathology*
  • Tumor Cells, Cultured


  • Carcinoembryonic Antigen
  • RNA, Messenger
  • Glyceraldehyde-3-Phosphate Dehydrogenases