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BRAF p.Val600Glu (V600E) somatic mutation is mainly associated with MSS phenotype in metastatic colorectal cancer.

BACKGROUND
Oncogenic activation of EGF-signalling pathway is central to the progression of colorectal cancer. The use of mutations of the KRAS codons 12 and 13 as a selection biomarker for anti-endothelial growth factor receptor (EGFR) monoclonal antibody treatment is at present the first major step towards individualised treatment for patients with metastatic colorectal cancer. The impact of BRAF V600E mutation is not well documented.


PATIENTS AND METHODS
A total of 803 metastatic cancer samples from colorectal cancer patients were explored for KRAS exon 2 and BRAF exon 15 mutations. BRAF mutated samples were characterized for mismatch repair function.


RESULTS
Overall, 344 tumours were mutated, with 34 of them involving BRAF mutations (8 of microsatellite instability type). No specificity was found according to gender, age at diagnosis and tumour localisation.


CONCLUSION
A complete analysis of KRAS, BRAF and PIK3CA status may identify approximately 10-15% additional patients who are unlikely to respond an EGFR-targeted monoclonal antibody and who may benefit from prospective and specific new biomarker-driven studies.