SMAD4 and NF1 mutations as potential biomarkers for poor prognosis to cetuximab-based therapy in Chinese metastatic colorectal cancer patients

Cetuximab, an anti-EGFR monoclonal antibody, is used in combination with chemotherapy in clinic to enhance the outcome in metastatic colorectal cancer (mCRC) patients with only ~ 20% response rate. To date only activating mutations in KRAS and NRAS have been identified as poor prognosis biomarkers in cetuximab-based treatment, which makes an urgent need for identification of novel prognosis biomarkers to precisely predict patients' response in order to maximize the benefit. In this study, we analysed the mutation profiles of 33 Chinese mCRC patients using comprehensive next-generation sequencing (NGS) targeting 416 cancer-relevant genes before cetuximab treatment. Upon receiving cetuximab-based therapy, patients were evaluated for drug response, and the progression-free survival (PFS) was monitored. The association of specific genetic alterations and cetuximab efficacy was analyzed. Patients carrying SMAD4 mutations (SMAD4 , n = 8) or NF1 mutations (NF1 , n = 4) had significantly shorter PFS comparing to those carrying wildtype SMAD4 (SMAD4 , n = 25) (P = 0.0081) or wildtype NF1 (NF1 , n = 29) (P = 0.0028), respectively. None of the SMAD4 or NF1 patients showed response to cetuximab when assessed at 12-week post-treatment. Interestingly, two patients carrying both SMAD4 and NF1 showed the shortest PFS among all the patients. Our results demonstrated that SMAD4 and NF1 mutations can serve as potential biomarkers for poor prognosis to cetuximab-based therapy in Chinese mCRC patients.