Abstract: Background and purpose: The incidence of BRAF mutation ranged from 5% to 15% among colorectal cancer according to previous studies, and was associated with poor survival. To evaluate safety, feasibilityand efficiency of BRAF inhibitor combined with epidermal growth factor receptor (EGFR) inhibitor for patient-derived xenografts (PDXs) of BRAF mutant recurrent and metastatic colorectal cancer. Methods: From Jan. 2016 to Dec. 2016, a total of 34 colorectal cancer patients were performed CT guided biopsy because of recurrence or metastasis indicated by image examination. PDXs models of recurrent and metastatic colorectal cancer were established by biopsy specimen. Screened the BRAF V600E mutant and cultivated to F2 generation for drug administration. The experimental group: BRAF inhibitor (Group A), EGFR inhibitor (Group B), BRAF and EGFR inhibitor (Group C). The control group: placebo (Group D). After three weeks, the efficiency was evaluated by tumor inhibition rate. Results: Twenty-three of the patients were confirmed recurrence or metastasis by pathology. Sixteen PDXs models were established, with success rate of 69.6% (16/23). Four BRAF V600E mutant patients were screened and PDXs models were established. There was no obvious drug toxicity related death in experimental group. The tumor inhibition rate of experimental group was 21.57%、21.61% and 66.81%, respectively. Group C had the most significant reduction of tumor volume (P<0.05). Conclusion: Combination of BRAF and EGFR inhibitor had high safety, feasibility and efficiency in PDXs of BRAF mutant recurrent and metastatic colorectal cancer.

Key words: Colorectal cancer, Recurrence and metastasis, BRAF mutation, Patient-derived xenografts model