Immune Therapy in Esophageal Cancer: A Rationale and Current Status

Esophageal cancer carries a poor prognosis within the United States and worldwide, with adenocarcinoma (EA) prevailing in the U.S. and the West as it is etiologically tied to rising obesity rates, associated acid reflux, and Barrett esophagus. However, the number afflicted with squamous cell carcinoma (ESCC) throughout the world is far greater than adenocarcinoma. ESCC is most prevalent in the Far East, including Japan and China, as well as in South Africa, Turkey, and Iran as it is etiologically tied to tobacco use, diets low in fresh fruit and vegetables, chemical preservatives in food, and exposure to the human papillomavirus (HPV) [1]. Surgical resection remains the gold standard of treatment for early tumors, but the addition of chemotherapy and radiation therapy has proven necessary for the control and enhanced survival of those presenting with locally advanced disease. While systemic cytotoxic chemotherapy is the chief option for the palliation of metastatic disease, immune checkpoint inhibitor therapy has emerged as a promising new therapeutic option as it has for several other malignancies. The theoretical basis for testing immune checkpoint inhibitor therapy for those with esophageal cancer rests with the tumor's association with mutagenic toxins and its increased mutational burden. Herein we review current results and ongoing studies seeking improved outcomes in patients with esophageal cancer treated with immune therapy.