ABSTRACT
@# Colorectal cancer (CRC) is the third most common malignancy and the fourth leading cause of cancer-related death all over the world. Traditional treatments, including chemotherapy, radiation therapy, surgery and targeted therapy, form the backbone of current treatment in various stages of CRC, but the efficacy in patients with recurrent or metastatic disease is extremely poor. Recently-developed immunotherapy is frequently used in various cancers with high malignancy, such as leukemia, melanoma and non-small-cell lung cancer, and achieves promising clinical outcomes. Immunotherapy has been also investigated in CRC, but the outcome is so disappointed in majority of patients, except the PD-1 inhibitor achieved excellent result in CRC with DNA mismatch repair system deficiency. In this review, the authors will mainly introduce the immunophenotype of different subtype of CRC and summarize current advances of clinical trials for CRC immunotherapy. The article will also discuss the reasons for the low efficacy of immunotherapeutic approaches in CRC and provide several potential directions for the future development of CRC immunotherapy.