Concordant analysis of KRAS status in primary colon carcinoma and matched metastasis

KRAS somatic mutations are the main predictive factor for non response to EGFR-targeted monoclonal antibodies in metastatic colorectal cancer (mCRC) patients. We compared KRAS mutational status in the primary tumour and the corresponding metastases (1 to 4 sites) in 38 mCRC patients. KRAS mutational status was analysed using direct sequencing, SNAPShot multiplex PCR and Scorpion Taqman PCR analysis. Results showed 54% of primary tumours had KRAS mutations. A concordance of 97% between primaries and metastatic sites was observed. A tumour heterogeneity was also demonstrated in 5% of mCRC. One case with three different primary tumours harboured three different KRAS mutations, and only one was represented in the unique metastasis of this patient. We concluded there was a high concordance in the KRAS status between the primary tumour and metastases. More than one informative block and more sensitive assay may increase the accuracy of KRAS status determination.