Gastrointestinal (GI)
cancers account for a large proportion of
cancer deaths worldwide and pose a major public health challenge.
Immunotherapy is considered to be one of the prominent and successful approaches in
cancer treatment in recent years. Among them,
immune checkpoint inhibitor (ICI)
therapy, has received widespread attention, and many clinical findings support the feasibility of ICIs, with sustained responses and significantly prolonged lifespan observed in a wide range of
tumors. However, patients treated with ICIs have not fully benefited, and therefore, the identification and development of
biomarkers for predicting ICI treatment response have received further attention and exploration. From
tumor genome to molecular interactions in the tumor microenvironment, and further expanding to circulating
biomarkers and patient characteristics, the exploration of
biomarkers is evolving with high-throughput sequencing as well as bioinformatics. More large-scale prospective and specific studies are needed to explore
biomarkers in GI
cancers. In this review, we summarize the known
biomarkers used in ICI
therapy for GI
tumors. In addition, some ICI
biomarkers applied to other
tumors are included to provide insights and further validation for GI
tumors. Moreover, we present single-cell analysis and machine learning approaches that have emerged in recent years. Although there are no clear applications yet, it can be expected that these techniques will play an important role in the application of
biomarker prediction.