Developments in immunotherapy for gastrointestinal cancer

Gastrointestinal (GI) cancers are the most commonly occurring cancer worldwide. Colorectal cancer (CRC) is the second and third most commonly diagnosed cancer in women and men, respectively. Despite the advent of screening and the declining incidence of CRC overall, most patients are not diagnosed at an early, localized stage. Due to resistance to chemotherapy, recurrence, and metastatic disease, those diagnosed with advanced disease have only a 12% 5-year survival rate. Given the overwhelming global impact of CRC, the need for advanced therapy is crucial. Targeted immunotherapy in addition to surgical resection, traditional chemotherapy, and radiation therapy is on the rise. For the purpose of this review, we focused on the advances of immunotherapy, particularly in CRC, with mention of research pertaining to particular advances in immunotherapy for other aspects of the GI system. We review basic immunology and the microenvironment surrounding colorectal tumors that lead to immune system evasion and poor responses to chemotherapy. We also examined the way these obstacles are proving to be the targets of tumor specific immunotherapy. We will present current FDA approved immunotherapies such as monoclonal antibodies (mAb) targeting tumor specific antigens, as well as vaccines, adoptive cell therapy, cytokines, and check-point inhibitors. A summation of prior research, current clinical trials, and prospective therapies in murine models help delineate our current status and future strategies on CRC immunotherapy.