Somatic mutation profiling and HER2 status in KRAS-positive Chinese colorectal cancer patients

KRAS is an independent negative predictor for anti-epidermal growth factor receptor (anti-EGFR) treatment in colorectal cancers (CRCs). However, 30% to 50% of CRC patients are KRAS-positive and do not benefit from anti-EGFR therapy. In this study, we investigated the mutational features and clinical significance of KRAS-positive Chinese CRC patients. A total of 139 Chinese CRC patients who received clinical KRAS testing (Sanger sequencing) were examined by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Fifty KRAS-positive specimens were further detected by next-generation sequencing (NGS). The most prevalent mutation in KRAS was G12D (46%), followed by G12V (20%), and G13D (18%). In addition to KRAS, 72 unique alterations in another 12 genes were also detected. The most common mutated genes were TP53 (62%), APC (46%), and PIK3CA (22%). The proportion of HER2 amplifications in KRAS-positive CRC patients was 4.4%, which was lower than that in KRAS -negative CRC patients (14.3%). No relationship was found between HER2 amplification and KRAS status (p = 0.052). However, the odds ratio is very low (0.279). In addition, these gene mutations were not significantly associated with age, sex, tumor size, lymph node metastasis, mismatch repair-deficient, or tumor differentiation. However, TP53 mutations were more prevalent in colon cancer with KRAS mutations than in rectal cancer (75.0% vs 28.6%, respectively, p = 0.004). The negative predictive value of the IHC analysis for predicting HER2 amplification reached to 98.39%, while the positive predictive value reached only 50%. Overall, the mutation profiling of Chinese CRC patients with KRAS mutations is different from that of Western CRC patients. Our results will help us to understand the molecular features of Chinese CRC patients.