Quantification of micrometastases in lymph nodes of colorectal cancer using real-time fluorescence polymerase chain reaction.

The expression of carcinoembryonic antigen (CEA) mRNA was assessed in 102 lymph nodes (LNs) obtained from seven colorectal cancer patients by both the conventional non-quantitative RT-PCR and quantitative RT-PCR. The number of CEA-expressing cells was calculated compared with CEA-expressing MKN-45 cell line as a standard control. Using the quantitative RT-PCR, the relative number of CEA-expressing cells ranged between 1.3x103 and 5.7x106 in 16 histologically positive LNs and between 2.3x101 and 8.1x105 in 10 histologically negative and RT-PCR positive LNs. In both histologically and RT-PCR negative LNs, the relative cell number was <4.0x102. Our results demonstrated that quantifying the amount of metastasis might enhance the reliability of RT-PCR detection assay as a diagnostic tool for the detection of cancer micrometastases.