Predicting and monitoring the treatment response of patients with esophageal carcinoma are important. Molecular analyses of biopsy specimens are useful; however, the characteristics of the biopsy specimen are not similar to those of whole tumors, including metastatic tumors. Therefore, liquid biopsy using blood samples has been applied for the prediction of the tumor stage, sensitivity to radiotherapy, sensitivity to chemotherapy, and recurrent disease. Liquid biopsy is advantageous for monitoring the treatment response and as an objective diagnostic tool; it is cost effective.