Abstract 3749: Usefulness of Transcription-Reverse Transcription Concerted (TRC) method in detecting circulating tumor cells of patients with colorectal cancer

Background: Owing to refinement of an immunomagnetic separation technology method for count and characterization of circulating tumor cells (CTCs) in patients with epithelial malignancies has been established. CellSearch System (CSS) is a device using this technology and the significance of CSS has been reported in various carcinoma. On the other hand, as a novel PCR based techniques, the amplification system with transcription-reverse transcription concerted reaction (TRC) method was introduced for detecting a few cancer cells. This method amplifies a cancer-specific messenger RNA (mRNA) directly in a single tube at a constant temperature without thermal cycling in three steps for PCR: denaturing, annealing, and extension. Accordingly, this method may produce a more stable and reliable result because of its simplified process compared to conventional PCR-based techniques. Another advantage of TRC method over CSS is the cost. It takes 30 dollars per sample in TRC method, while the cost of CSS is 800 dollars per sample. Object: In this study, we have investigated the utility of TRC method which targeted CEA-mRNA in detecting CTCs of patients with colorectal cancer. Materials and Methods: Between Nov. 2008 and May 2009, 42 samples from metastatic and/or recurrent colorectal cancer patients (mCRC) were enrolled. We compared the detection rate of CTCs between TRC method and CSS. In CSS, CTC was considered as positive when at least one cancer cell was detected. On the other hand, in TRC method, CTCs was considered as positive when the result of TRC method was positive. The statistical significance was evaluated by chi-square test. Differences were considered to be statistically significant when the p-value was less than 0.05. Results: In CSS, 27 samples (64.3%) were CTC positive, while 16 samples (38.1%) were CTC positive by TRC method. All of samples which are CTC positive by TRC method were also CTC positive by CSS. In order to compensate the lower sensitivity of TRC method, we have taken serum CEA value into account. As a result, all samples negative for TRC method but positive for CSS were from the patients whose serum CEA value was more than 20 ng/ml. In contrast, when serum CEA value of the patients was less than 20 ng/ml, all samples negative for TRC method demonstrated CTC negative for CSS. These results indicate that CSS should be done only when the sample from patients whose serum CEA value is more than 20 ng/ml is negative for TRC method. Conclusions