Discordant quantitative detection of putative biomarkers in nodal micrometastases of colorectal cancer: biological and clinical implications

Aims: Nodal expression of the carcinoembryonic antigen ( CEA), cytokeratin 20 ( CK20), and guanylyl cyclase C ( GCC) genes was measured in tandem in patients with colorectal cancer ( CRC) to assess whether there would be sufficient agreement between these markers in their ability to detect micrometastasis to qualify one of them as a universal marker, and whether frozen and paraffin wax embedded tissues would yield similar results. Methods: One hundred and seventy five frozen lymph nodes ( FT) and 158 formalin fixed, paraffin wax embedded lymph nodes ( PET) from 28 CRC cases were analysed using gene specific quantitative real time polymerase chain reaction, carried out on the LightCycler(R) system with SYBR Green chemistry. Results: There was significant disparity in positive detection of the three biomarkers in FT versus PET, with notable agreement achieved only for CEA ( 66.6%) in FT versus PET in Dukes' B disease, and between CK20 and GCC ( 44.6%) in FT, also in Dukes' B disease. One patient with full concordance in all three tumour markers with both tissue types suffered a relapse and died within two years of follow up. Conclusions: There was considerable discordance in the positive detection of the three tumour markers in both tissue types ( FT versus PET). This brings into question whether using a single tumour marker to detect micrometastasis in one tissue type ( FT or PET) is adequately representative, and challenges the concept of universal markers for molecular CRC metastatic detection. Multiple tumour markers would predict more accurately the metastatic potential of Dukes' B CRCs.