Correlation between clinicopathological features and KRAS, NRAS, and BRAF mutation status in Chinese colorectal cancer patients

This study was retrospectively performed to analyze correlations between clinicopathological features of colorectal cancer (CRC) and mutations in KRAS, NRAS, and BRAF in Chinese patients, and to assess the importance of detecting additional mutations in KRAS exons 3 and 4 and NRAS in patients with CRC. RAS (KRAS and NRAS) and BRAF mutations were detected in 715 and 655 patients respectively. The mutation rate of RAS (KRAS or NRAS) was 45.6% (326/715). KRAS exon 2 mutations were evaluated in 36.6% of patients (262/715). Additional mutations in RAS exons occurred in 9.0% of patients (64/715), including KRAS exons 3 and 4 in 5.6% (40/715) and NRAS exons 2, 3, or 4 in 3.4% (24/715). Among 453 patients with wild-type KRAS exon 2, 14.1% (64/453) had other mutations in RAS exons. The most frequent sites of mutations were codons 12, 13, 61, and 146 in KRAS and codons 12 and 61 in NRAS. The mutation rate of BRAF (exon 15) was 4.0% (26/655), and the most frequent mutation site was codon 600. Among 440 patients with CRC who had a primary tumor resection at our center, those with mucinous or signet ring cell CRC were more likely to harbor KRAS mutations than those with adenocarcinoma (62.7% vs. 43.6%, P=0.006 and 59.3% vs. 39.6%, P=0.004, respectively). Female patients had a higher BRAF (exon 15) mutation rate than male patients (5.1% vs. 1.1%, P=0.017). Detection of both KRAS and NRAS mutations is useful for selecting patients who will benefit from anti-EGFR monoclonal antibody therapy. KRAS mutations were more frequent in patients with mucinous adenocarcinoma/signet ring cell CRC, whereas BRAF mutations were more common in female patients with CRC.