Direct sequencing is a reliable assay with good clinical applicability for KRAS mutation testing in colorectal cancer

BACKGROUND: The analysis of KRAS mutations in colorectal cancer (CRC) has made the need urgent for a reliable and easy to implement assay in daily practice. OBJECTIVE: This study was designed to compare the different assays for KRAS testing and elucidate its mutation status in Chinese CRC patients. METHODS: Direct sequencing was conducted to detect mutations in KRAS codons 12, 13 and 61 using 574 colorectal paraffin embedded clinical samples. And a subset of 66 samples was further detected independently by a commercial kit for comparison of different assays. RESULTS: KRAS codons 12 and 13 mutations were detected in 40.9 and 42.4% of 66 CRC samples using the kit and direct sequencing methods, respectively. The concordance between two methods reached 95.5% (Kappa = 0.907, P < 0.001). Workload and time to results were comparable for both. Moreover, KRAS mutations were detected in the total 574 CRC tumors by direct sequencing as followed: 25.3% in codon 12, 6.8% in codon 13, and 2.1% in codon 61. Notably, the mutations were more frequent in females than males, and patients older than 60 years exhibited higher rates of mutation (P < 0.05). CONCLUSIONS: Direct sequencing showed similar mutation rate as the detection kit and hence can be used effectively and reliably for clinical screening of somatic tumor gene mutations.