Colorectal Cancer with EML4-ALK Fusion Gene Response to Alectinib: A Case Report and Review of the Literature

Anti-epithelial growth factor receptor or anti-vascular endothelial growth factor agents combined with chemotherapy were the standard of treatment for metastatic colorectal cancer (CRC). However, increasing evidence of molecularly stratified treatment makes the complexity of treatment. Anaplastic lymphoma kinase (ALK) gene alternation is one of potential target for biomarker-guided therapy for CRC. We present a case of a 56-year-old man who suffered from advanced ascending colon cancer, harboring echinoderm microtubule associated protein-like 4 (EML4)-ALK fusion gene E21; A20 variant, a rare variant in EML4-ALK fusion gene in lung cancer. We also detected this fusion gene from different tissue types including circulating tumor DNA (ctDNA) and ascites fluid. The patient was offered alectinib, an ALK inhibitor, with partial response in lung, liver, and peritoneal metastasis for 8 months. Tumor heterogeneity, especially in gastrointestinal tract cancer, raise our interest in comprehensive genetic profiling in clinical practice. Convenience and reliability of next-generation sequencing, including using ctDNA, help physicians deal with clinical dilemma. ALK-positive CRC is rare. However, advanced CRC with ALK gene alteration responds to ALK inhibitor. It is reasonable to check ALK gene alteration in clinical practice for CRC.