RAS status in Korean patients with stage III and IV colorectal cancer.

Background: KRAS mutations are common and clearly contribute to malignant progression. The frequency of NRAS mutations and their relationship to clinical, pathologic, and molecular features remains unclear.
Methods: We evaluated 130 colorectal tumors for mutations in KRAS and NRAS gene. We tested for mutations in codons 61 and 146 of KRAS and codons 12, 13, 59, 61 and 146 of NRAS. Mutation status was determined by targeted dideoxy sequencing.
Results: Among the analyzed primary tumors, 36.2% had KRAS mutation. Of the 83 KRAS codon 12 and 13 wild-type patients, 7.2% had KRAS codon 61, 146 or NRAS. 40.7% harbored any RAS mutation.
Conclusion: The frequency of other RAS (NRAS and KRAS exon 3, 4) activating mutations in colorectal cancers is relatively low in Korean colorectal cancer patients.