Background: RAS/BRAF V600E mutations are the most remarkable oncogenic driver mutations in colorectal cancer (CRC) and play an important role in treatment selection. No data are available regarding the clinical and prognostic features of patients with detailed RAS/BRAFV600E-mutant metastatic CRC (mCRC) in Japan.
Methods: Chemotherapy-naïve patients with mCRC were included in this study between August 2018 and July 2019. Tumor samples were collected, and RAS/BRAFV600E status was investigated. RAS/BRAFV600E status was examined using a MEBGEN RASKET-B kit and polymerase chain reaction reverse sequence-specific oligonucleotide method.
Results: RAS/BRAF V600E mutations were detected in 54% of cases (KRAS codon 12 = 26%; KRAS codon 13 = 11%; minor RAS [non-KRAS codon 12 and non-KRAS codon 13] = 10%; and BRAFV600E = 7%). BRAFV600E-mutant CRC mainly existed in the right colon, whereas minor RAS-mutant CRC was predominantly present in the left colon. Minor RAS-mutant CRC was associated with shorter survival time than RAS wild-type CRC (hazard ratio [HR] = 2.45; 95% confidence interval [CI] = 0.92–6.57; p = 0.073) and significantly shorter overall survival than major RAS-mutant CRC (HR = 4.77; 95% CI = 1.44–15.77; p = 0.010). The KRAS codon 12 mutant group showed significantly longer overall survival than the minor RAS mutant groups (HR = 0.06; 95% CI = 0.01–0.47; p < 0.00) and had extended progression-free survival compared with the codon 13 group.
Conclusions: In our multicenter study, the findings elucidated the clinical and prognostic features of patients with detailed RAS/BRAFV600E-mutant mCRC in Japan.