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. Exons 2-4 KRAS/NRAS, BRAF, PIK3CA molecular evaluation was performed with RT-PCR and Sequenom.


RESULTS
From 165 deemed adequate by the pathologist pairs, 85 (51.5%) were concordantly mutated in at least one of the tested genes, 70 (42.5%) were wt and 10 (6%) were discordant, harbouring a mutation in the primary and not in the endoscopic biopsy. In the re-evaluation, when more slides were cut per discordant pair, mutational status changed in two of the six discordantly KRAS-mutated pairs. A strong strength of agreement for both runs was observed (Cohen's kappa, k=0.877, P<0.001 and k=0.901, P<0.001, respectively) between the surgically acquired and the endoscopic biopsy specimens' evaluation.


CONCLUSIONS
Based on our results, an endoscopic biopsy could provide an accurate mutational profile and become a justified alternative to a surgically removed primary tumour specimen, as long as specific histopathology criteria are met.
Laboratory of Tumor Cell Biology, School of Medicine, University of Crete, Voutes 71110, Heraklion, Greece.|Department of Oncology, Laboratory of Molecular Digestive Oncology, Katholieke Universiteit Leuven, Leuven, Belgium.
Z
Z
Saridaki
Center for Translational Cell and Tissue Research KU Leuven, Minderbroederstraat 12 3000 Leuven, Belgium.
X
X
Saegart
Department of Oncology, Laboratory of Molecular Digestive Oncology, Katholieke Universiteit Leuven, Leuven, Belgium.
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V
De Vriendt
Laboratory of Tumor Cell Biology, School of Medicine, University of Crete, Voutes 71110, Heraklion, Greece.
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D
Hatzidaki
Center for Translational Cell and Tissue Research KU Leuven, Minderbroederstraat 12 3000 Leuven, Belgium.
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S
Palmans
Center for Translational Cell and Tissue Research KU Leuven, Minderbroederstraat 12 3000 Leuven, Belgium.
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L
De Smedt
Department of Imaging and Pathology, Translational Cell and Tissue Research, KU Leuven, Leuven, Belgium.
G
G
De Hertogh
Department of Oncology, Laboratory of Molecular Digestive Oncology, Katholieke Universiteit Leuven, Leuven, Belgium.|University Hospitals Leuven and KU Leuven, Leuven, Belgium.
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S
Tejpar
D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy / Q000592:standards; D058534:Class I Phosphatidylinositol 3-Kinases; D003113:Colonoscopy / Q000592:standards*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D004252:DNA Mutational Analysis; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics*; D020869:Gene Expression Profiling / Q000379:methods; D011905:Genes, ras; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction
D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human