Clinical Development of PD-1/PD-L1 Immunotherapy for Gastrointestinal Cancers: Facts and Hopes.

Gastrointestinal (GI) cancers are among the most deadly malignancies. Although serial incremental survival benefits have been made with cytotoxic chemotherapy with metastatic disease, a plateau of achievement has been reached. Applying modern integrative genomic technology, distinct molecular subgroups have been identified in GI cancers. This not only highlighted the heterogeneity in tumors of each primary anatomical site but also identified novel therapeutic targets in distinct molecular subgroups and might improve the yield of clinical success. Molecular characteristics of tumors and their interaction with the tumor microenvironment would further affect development of combination therapy, including immunotherapy. Currently, immune checkpoint blockade attracts the most intense research, and the successful integration of these novel agents in GI cancers in the treatment paradigm requires an in-depth understanding of the diverse immune environment of these cancers. .