Immunotherapy for Gastrointestinal Malignancies

Gastrointestinal (GI) malignancies comprise esophageal, stomach, liver, biliary tract, pancreatic, small bowel, appendiceal, colorectal, and anal cancer. All of them originate from the GI tract; however, their disease course and management vary significantly. To date, only a small number of GI cancers respond well to immunotherapy that has been approved by the US Food and Drug Administration. Their different sensitivity to immunotherapy may be due to the type of cancer cells involved (e.g., adenocarcinoma versus squamous cell carcinoma), primary location of the cancer (e.g., pancreatic versus anal cancer), potential causes of cancer (e.g., acid reflux for esophageal cancer versus bacterial infection for stomach cancer), and so on. Altogether, these factors shape the interactions among cancer cells, immune cells, and adjacent normal cells, which ultimately determine the treatment response to immunotherapy. In this chapter, we will discuss the current state of immunotherapy in the field of GI cancers by reviewing the most pertinent concept and landmark clinical trials that guide the use of immunotherapy to treat GI cancers.