KRAS and metastatic neoplasm: Although numerous methods have been developed for determining KRAS mutation status in CRC patients, they are largely dependent on the quality and quantity of tumor tissues8 and the data turnaround time is long (2‐3 weeks).9 In addition, tumor tissues especially metastatic tumors are rarely available for testing because of practical and ethical reasons.10, 11 Thus, for determining KRAS mutation status, we need a feasible and sensitive biomarker.