PD-1 and PD-L1 blockade in gastrointestinal malignancies

- PD-1 and PD-L1 blockade represent a major breakthrough in cancer therapy.
- Background, preclinical and phase I studies involving GI patients are discussed.
- Evidence summarised according to GI primary tumour site; GI toxicities reviewed.
- Potential biomarkers of response to PD-1 and PD-L1 are discussed and evaluated.
- PD-1 and PD-L1 blockade in combination with other therapies are explored in-depth.

Immunotherapy represents a major breakthrough in cancer therapy in recent years. Immune-checkpoint blockade using PD-1 and PD-L1 antibodies appears to be one of the most promising immunotherapy approaches. Immunotherapy differs from conventional cancer treatment because of its ability to produce durable responses in some patients.In this review article, we explore the available evidence and summarise current clinical trials for PD-1 and PD-L1 blockade in gastrointestinal malignancies. The challenge now is to develop strategies to increase the efficacy of PD-1 and PD-L1 blockade in gastrointestinal cancer patients, such as combination therapy with chemotherapy, radiotherapy or other immunotherapy, along with validating biomarkers to select patients and personalise treatment.