Immune checkpoint inhibitors in luminal gastrointestinal malignancies: going beyond MSI-H/dMMR, TMB and PD-L1.

Immune checkpoint inhibitors (ICIs) are medications that help the natural immune system fight cancer cells, preventing their growth. In tumors of the gastrointestinal tract, mounting research has shown that ICIs are useful in treatment regimens. However, this depends on certain characteristics of individual cancers, such as how many mutations they have, if they are missing certain enzymes and other considerations. ICIs can also be paired with standard ­ and nonstandard ­ treatments like chemotherapy, radiation and other targeted therapy to increase their effectiveness against cancer. This article discusses how ICIs are used in gastrointestinal tract cancers according to the available evidence in the medical literature, and it explores the directions of the research on the forefront of immunotherapy.