**4. Conclusions and future directions**

The success of immunotherapy in some tumors came from years of research deep into the immune system and tumor itself and brought hope of healing cancer. It is worth mentioning that several immune checkpoint blockers have been or are being approved by the FDA, and it is expected that the next step will be to accelerate the pace of application of single drug or other treatment modes in combination within clinical usage. However, opportunities and challenges coexist, and there are still some key questions that have not been answered in immunotherapy. First of all, many targeted cancer drugs that treat cancer need to be explored to determine the biological dose that achieves the greatest clinical benefit with minimal toxicity. Second, given that most of the current immunotherapy is mainly to activate anti-tumor effects by activating the immune system, this kind of treatment requires patient to have some degree of immunity before receiving the initial immunotherapy. Therefore, it is imperative to fully evaluate patient's immune status and find biomarkers that predict the effectiveness of immunotherapy. In addition, there is abundant evidence that exposure to radiation and chemotherapy drugs may affect the rate of DNA mutations in tumor cells, prompting the formation of some new antigens. As the current immunotherapy is always combined with radiotherapy and chemotherapy, determining the proper dose for each regimen is the prerequisite for maximum benefit of combined therapy.

Immunotherapy has a broad application prospect in the treatment of malignant tumors. The high frequency of esophageal cancer mutations and the effective results of immunotherapy highlighted in other gastrointestinal cancers provide strong evidence for the study of esophageal cancer immunotherapy. Treatment strategies combined with existing or new treatment modes will be the direction of future esophageal cancer treatment.
