Colorectal cancer is one of the most common malignant
tumors and, hence, has become one of the most important public health issues in the world. Treatment with
immune checkpoint inhibitors (ICIs) successfully improves the survival rate of patients with
melanoma,
non-small-cell lung cancer, and other
malignancies, and its application in metastatic
colorectal cancer is being actively explored. However, a few patients develop drug resistance. Predictive molecular markers are important tools to precisely screen patient groups that can benefit from treatment with ICIs. The current article focused on certain important predictive molecular markers for ICI treatment in
colorectal cancer, including not only some of the mature molecular markers, such as deficient mismatch repair (d-MMR),
microsatellite instability-high (MSI-H),
tumor mutational burden (TMB), programmed death-ligand-1 (PD-L1),
tumor immune microenvironment (TiME), and tumor-infiltrating lymphocytes (TILs), but also some of the novel molecular markers, such as
DNA polymerase epsilon (POLE), polymerase delta 1 (POLD1), circulating tumor DNA (ctDNA), and consensus molecular subtypes (CMS). We have reviewed these markers in-depth and presented the results from certain important studies, which suggest their applicability in CRC and indicate their advantages and disadvantages. We hope this article is helpful for clinicians and researchers to systematically understand these markers and can guide the treatment of
colorectal cancer.