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

BACKGROUND: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. METHODS: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. RESULTS:Patients carrying SMAD4 mutations (SMAD4mut, n = 8) or NF1 mutations (NF1mut, n = 4) had significantly shorter PFS comparing to those carrying wildtype SMAD4 (SMAD4wt, n = 25) (P = 0.0081) or wildtype NF1 (NF1wt, n = 29) (P = 0.0028), respectively. None of the SMAD4mut or NF1mut patients showed response to cetuximab when assessed at 12-week post-treatment. Interestingly, two patients carrying both SMAD4mut and NF1mut showed the shortest PFS among all the patients. CONCLUSIONS:Our results demonstrated that SMAD4 and NF1 mutations can serve as potential biomarkers for poor prognosis to cetuximab-based therapy in Chinese mCRC patients.