Current state of the art: immunotherapy in esophageal cancer and gastroesophageal junction cancer

Esophageal cancers have a high mortality rate and limited treatment options especially in the advanced/metastatic setting. Squamous cell carcinoma (SCC) and adenocarcinoma are two distinct types of esophageal cancer. Esophageal SCC is more common in nonindustrialized countries with risk factors including smoking, alcohol use, and achalasia. Adenocarcinoma is the predominant esophageal cancer in developed nations, and risk factors include chronic gastroesophageal reflux disease, obesity, and smoking. Chemotherapy has been the mainstay of therapy for decades until immunotherapy made its debut in the past few years. Immune checkpoint inhibitors have been tested in many studies now and are becoming an essential component of esophageal cancer treatment. Monoclonal antibodies that selectively inhibit programmed cell death-1 (PD-1) activity such as pembrolizumab and nivolumab, have become standard of care in the treatment of esophageal cancer. Several other anti-PD-1 antibodies like camrelizumab, toripalimab, sintilimab, trislelizumab are under investigation in different stages of clinical trials. Here we provide a comprehensive review of extant literature as well as ongoing trials with various combinations of chemotherapy or other targeted therapy with a focus on different histological subgroups of esophageal cancer and in different clinical settings.