Rapid Quantitative Detection of Free Cancer Cells
in the Peritoneal Cavity of Gastric Cancer Patients
with Real-Time CEA RT -PCR Using Hybridization Probes
HAYAO NAKANISHI*, YASUHIRO KODERA, MASAE TATEMATSU
Introduction
Detection of free cancer cells in the abdominal cavity has important prognostic
implications for cancer of the stomach, pancreas, and ovary. Cytology examination of peritoneal washes has been the gold standard, and its clinical relevance is
now recognized worldwide. The conventional method, however, is reported to
lack sensitivity and patients with negative cytology results may nevertheless present with recurrent peritonitis carcinomatosa.
The recently introduced reverse-transcriptase polymerase chain reaction (RTPCR) has demonstrated sensitive detection of micro metastases in the peritoneal
cavity [1, 2]. Since carcinoembryonic antigen (CEA) is a specific marker for
epithelial cells in peritoneal washes and the expression at the mRNA level is maintained in the majority of gastric cancers, it is recognized as a reliable target gene
for detection of tumor cells with RT -PCR [3]. Despite such distinct advantages in
terms of sensitivity, however, the RT-PCR analysis has the following shortcomings: (1) it is only qualitative and lacks quantitative assessment of risk of peritoneal recurrence; (2) a certain proportion of false-positive RT-PCR results
appears to have been generated with a subsequent uneventful clinical course; and
(3) gene amplification and subsequent data analysis are time-consuming and
consequently the results of RT-PCR are not available during surgery.
To overcome these problems, we developed a rapid and quantitative method
for detection of free cancer cells in peritoneal washes using a new generation of
thermal cycler (the LightCycler system) with a hybridization probe format [4,5].
This rapid cycle real-time PCR system allows quantification of the initial template
copy number based on the inverse correlation between the cycle number at which
the sample fluorescence exceeds the background level and the starting copy number. Consequently, real-time RT-PCRwith the LightCycler instrument was found
to be a sensitive, quantitative, specific and rapid method for detecting free cancer
cells in peritoneal washes of patients with gastric cancer and has great promise
for routine use in the clinical setting.
* Hayao Nakanishi (~) (e-mail: hnakanis@aichi-cc.jp)
Division of Oncological Pathology, Aichi Cancer Center Research Institute, Chikusa-ku,
Nagoya 464-8681, Japan
in the Peritoneal Cavity of Gastric Cancer Patients
with Real-Time CEA RT -PCR Using Hybridization Probes
HAYAO NAKANISHI*, YASUHIRO KODERA, MASAE TATEMATSU
Introduction
Detection of free cancer cells in the abdominal cavity has important prognostic
implications for cancer of the stomach, pancreas, and ovary. Cytology examination of peritoneal washes has been the gold standard, and its clinical relevance is
now recognized worldwide. The conventional method, however, is reported to
lack sensitivity and patients with negative cytology results may nevertheless present with recurrent peritonitis carcinomatosa.
The recently introduced reverse-transcriptase polymerase chain reaction (RTPCR) has demonstrated sensitive detection of micro metastases in the peritoneal
cavity [1, 2]. Since carcinoembryonic antigen (CEA) is a specific marker for
epithelial cells in peritoneal washes and the expression at the mRNA level is maintained in the majority of gastric cancers, it is recognized as a reliable target gene
for detection of tumor cells with RT -PCR [3]. Despite such distinct advantages in
terms of sensitivity, however, the RT-PCR analysis has the following shortcomings: (1) it is only qualitative and lacks quantitative assessment of risk of peritoneal recurrence; (2) a certain proportion of false-positive RT-PCR results
appears to have been generated with a subsequent uneventful clinical course; and
(3) gene amplification and subsequent data analysis are time-consuming and
consequently the results of RT-PCR are not available during surgery.
To overcome these problems, we developed a rapid and quantitative method
for detection of free cancer cells in peritoneal washes using a new generation of
thermal cycler (the LightCycler system) with a hybridization probe format [4,5].
This rapid cycle real-time PCR system allows quantification of the initial template
copy number based on the inverse correlation between the cycle number at which
the sample fluorescence exceeds the background level and the starting copy number. Consequently, real-time RT-PCRwith the LightCycler instrument was found
to be a sensitive, quantitative, specific and rapid method for detecting free cancer
cells in peritoneal washes of patients with gastric cancer and has great promise
for routine use in the clinical setting.
* Hayao Nakanishi (~) (e-mail: hnakanis@aichi-cc.jp)
Division of Oncological Pathology, Aichi Cancer Center Research Institute, Chikusa-ku,
Nagoya 464-8681, Japan