Durable response to third-line combination therapy in a metastatic colorectal cancer patient with BRAF V600E mutation: A case report

In metastatic colorectal cancer (mCRC), the BRAFV600E mutation subtype is one of the subtypes with the worst prognosis. The long-term abnormal activation of multiple signaling pathways caused by the BRAF V600E mutation is closely related to the formation of BRAF inhibitor resistance and drug-resistant tumor cell subpopulations. These factors significantly impact the survival and prognosis of CRC patients. Therefore, treating mCRC patients with the BRAFV600E mutation, particularly in later stages, is challenging. We reported a case of an mCRC patient with the BRAF V600E mutation in the primary and metastatic tumors. After the failure of second-line treatment, this patient received a combination therapy including immunotherapy (tislelizumab), radiotherapy, and targeted therapy (fruquintinib). Through comprehensive imaging evaluations and continuous monitoring of tumor markers, we were astonished to observe that the patient has achieved and maintained a complete response (CR) for over 12 months. This case supports the efficacy of combination therapy in mCRC patients with the BRAF V600E mutation.