PS2-11: Validation of KRAS Mutation Testing Across Five Certified Laboratories

Abstract

KRAS mutation testing helps oncologists decide whether patients diagnosed with metastatic colorectal cancer (CRC) should be treated with epidermal growth factor receptor (EGFR) inhibitors. These drugs block the EGFR signaling pathway in tumor cells, and thus can slow tumor progression. Mutated KRAS is found in 30–45% of all CRC tumors, with mutations occurring at codons 12 and 13 being the most common. Patients with a mutated KRAS found in tumor tissue show limited clinical response to EGFR inhibitor therapy. Several factors can influence the results of KRAS mutation testing in tumor specimens. Variation can result from tumor heterogeneity, sample handling, DNA preparation, and differences in assay design and methodology. The purpose of this study was to evaluate comparability of KRAS test results among five labs currently used to determine KRAS mutation status of colorectal cancer specimens in a large multi-center study. Three commercial labs (Genzyme, Clarient, Quest Diagnostics), one clinical lab (Henry Ford Health System), and one research lab (Oregon Health Sciences University) were contracted to analyze KRAS mutational status; all are Clinical Laboratory Improvement Amendments (CLIA) certified. Twenty formalin-fixed paraffin-embedded (FFPE) human CRC samples that had been previously tested for KRAS mutations were selected based on mutation status (7 wild type samples, 7 with codon 12 mutations, and 6 with codon 13 mutations) from two clinical settings (Kaiser Permanente Colorado and Northwest). To ensure sufficient sample quantity, only surgical specimens from colon resections were used. Before being sent to each lab, the FFPE samples were reviewed by a pathologist to determine that the sample was of sufficient quality and quantity for testing. We asked each lab to use their standard clinical testing procedures. Clarient uses a polymerase chain reaction (PCR) method for mutation detection, Genzyme uses single nucleotide primer extension assay with fragment analysis by capillary electrophoresis, and the other three labs all use sequencing. Preliminary data (n=11 samples tested to date) suggests good agreement across laboratories despite differences in mutation detection methodologies.