A Rare EGFR–SEPT14 Fusion in a Patient with Colorectal Adenocarcinoma Responding to Erlotinib

Colorectal cancer (CRC) is the second leading cause of cancer death worldwide. Growing evidence supports gene fusions as good candidates for molecularly targeted therapy in CRC. Here we describe a case of a 63-year-old man who had a radical right hemicolectomy procedure 24 months ago. Pathological diagnosis indicated colorectal adenocarcinoma with stage pT4N2bMx. During re-examination in December 2016, positron emission tomography/computed tomography scans indicated relapse with multiple lymph nodes metastasis. Then the patient received a nine-cycle combination treatment of XELOX and bevacizumab and showed progressive disease (PD). Subsequently, the patient was treated with bevacizumab plus FOLFIRI for 2 months before discontinuation because of adverse events. Paraffin sections of postoperative colorectal tissue were subjected to next-generation sequencing, and epidermal growth factor receptor (EGFR) amplification and rare EGFR–SEPT14 fusion were identified. The patient then received erlotinib, an EGFR tyrosine kinase inhibitor (TKI), and achieved a partial response. However, the patient subsequently showed PD, and a new variant, EGFRvIII, appeared in metastasis, which may be involved in erlotinib resistance. We suggest that there is value in treating patients harboring EGFR fusions with EGFR TKI therapy, and EGFR–SEPT14 fusion may be used as a therapeutic target for CRC. Key Points: To the authors' knowledge, this is the first report of EGFR–SEPT14 fusion in colorectal cancer. The patient achieved a partial response after treatment with the epidermal growth factor receptor tyrosine kinase inhibitor erlotinib. This report expands the list of gene fusions in colorectal cancer and highlights new targets for the therapeutic intervention. EGFRvIII may be involved in erlotinib resistance, which is rare in colorectal cancer.