Complete Response to Pembrolizumab in Advanced Colon Cancer Harboring Somatic POLE F367S Mutation with Microsatellite Stability Status: A Case Study

BACKGROUND: Polymerase epsilon (POLE) mutations are considered as one of the most potential and promising biomarkers for immune checkpoint inhibitors (ICIs) in patients with colorectal cancer. However, the treatment of ICIs sometimes also resulted in unsatisfactory results in patients with POLE mutations, which revealed that not all mutations on POLE contribute to tumor regression in colorectal cancer. CASE PRESENTATION: We herein reported a case in which the patient with advanced colon cancer harboring somatic POLE F367S mutation, along with microsatellite stability status, has achieved efficacy of complete response to the programmed cell death 1 (PD-1) receptor inhibitor pembrolizumab, as well as a progression-free survival more than 49 months, and still in extension. CONCLUSION: Somatic POLE F367S mutation might be presented as a sensitive predictor to pembrolizumab in patients with colon cancer.