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

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.

This study was designed to compare the different assays for KRAS testing and elucidate its mutation status in Chinese CRC patients.

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.

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).

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.