Mutations in K-ras and Epidermal Growth Factor Receptor Expression in Korean Patients With Stages III and IV Colorectal Cancer

Abstract

K-Ras somatic mutations in advanced colorectal cancer (CRC) can predict resistance to mAbs that target the epidermal growth factor receptor (EGFR). The relationships between K-ras mutations and the EGFR status have not yet been examined, especially in Korean patients. A total of 82 colorectal tumors (stage III-IV) were analyzed. K-Ras mutations at codons 12 and 13 were detected by polymerase chain reaction—single strand conformational polymorphism. The EGFR expressions were examined by immunohistochemistry, and these were graded according to a modified EGFR expression scoring system. The relationships between the patients’ characteristics and the survival time and the gene mutation status were analyzed. The EGFR expression was positive in 69 patients (84.1%) and negative in 13 patients (15.9%). The K-ras mutation rate was 35.4%. In all, 20 (68.9%) cases were mutated at codon 12 and 9 (31.1%) cases were mutated at codon 13. No relationship was observed between the EGFR status and K-ras mutation. The median overall survival (OS) was 68.1 months. There was no difference between the K-ras mutant group and the wild type group for overall survival (30.3% vs 21.0%, respectively, at 36 months, P = .777). K-ras mutation and the EGFR status were not independent prognostic factors for OS (P = .105 and P = .499, respectively). For the Korean patients with CRC, the rate of an EGFR protein expression was greater than that for the patients in Western countries, and the rate of K-ras mutations was lower than that for patients in Western countries. This study found no correlation between the EGFR status and K-ras mutations in colorectal tumors.