KRAS, NRAS, BRAF mutation comparison of endoscopic and surgically removed primary CRC paired samples: is endoscopy biopsy material adequate for molecular evaluation?

Background: An everyday clinical practice dilemma in the 20-30% of metastatic colorectal cancer (CRC) patients that have not been operated on their primary tumour, is, under which specific histopathology and molecular circumstances, an endoscopic biopsy could be considered adequate to provide a representative RAS/BRAF molecular status to guide treatment.

Methods: A consecutive series of 193 paired biopsy and primary CRC tumour samples between August 2008 and 2010 available in the Department of Pathology archives, University Hospitals, KU Leuven were retrieved. For a pair to be included, in the endoscopic biopsy, 20% of invasive adenocarcinoma cells should be present and enough slides to yield an extracted DNA concentration of ⩾5 ng μl(-1), and no <2 ng μl(-1) should be available for cutting.