Current status of immune checkpoint inhibitor therapy for advanced esophageal squamous cell carcinoma.

Esophageal cancer is the seventh most common cancer, with an estimated 572,000 new cases, and the sixth most common cause of cancer-related deaths in 2018 with 509,000 annual worldwide deaths. Advanced esophageal squamous cell carcinoma (ESCC) is one of devastating tumors with a 5-year survival rate of less than 5% in patients with metastatic disease. Treatment options for patients with advanced ESCC are limited. Current guidelines recommend chemotherapy containing a platinum and a fluoropyrimidine agent as a first-line treatment. Recently, immune checkpoint inhibitors (ICIs), including nivolumab and pembrolizumab, have demonstrated antitumor activity and clinical efficacy in patients with advanced ESCC that is refractory or intolerant to first-line chemotherapy. ICIs are game-changers that not only transformed oncological strategy but also have a wide range of clinical potential in combination with conventional cytotoxic chemotherapy and radiotherapy. There is still an urgent, unmet need for reliable treatment options to conquer this intractable disease.