Current progress of immune checkpoint inhibitors for advanced colorectal cancer: concentrating on the efficacy improvement.

Abstract

Immune checkpoint inhibitors (ICIs) have paved a new pathway and revolutionized cancer treatment. Currently, ICIs have been extensively used for patients with advanced colorectal cancer (CRC), especially those harboring microsatellite instability (MSI). However, the efficacy of ICIs varies tremendously in different individuals, and some patients may not benefit from ICIs, which limits their clinical application. How to improve the efficacy of ICIs is an important issue to be solved. On the one hand, it is urgent to discover the predictive biomarkers to accurately screen the patients who gain benefit from ICIs, like microsatellite stability, tumor mutation burden (TMB), DNA polymerase ε/DNA polymerase δ1 mutations, and the expression of programmed death-ligand 1 (PD-L1). The rational use of these biomarkers will help clinicians identify suitable candidates who will benefit from ICI treatment, thereby improving therapeutic efficiency. Additionally, it is vital to design combination therapeutic strategies for optimizing the therapeutic effectiveness of ICIs. Nowadays, treatment strategies like chemotherapy, radiotherapy, targeted therapy along with ICIs, have helped improve the therapeutic effectiveness of ICIs. In this review, we have focused on the recent advancements in the predictive biomarkers and combination therapeutic strategies with ICIs for colorectal cancer.