PD-L1 evaluation in the gastrointestinal tract: from biological rationale to its clinical application

Area of Science:

• Oncology
• Immunology
• Gastroenterology

Background:

• Immune-checkpoint inhibitors targeting the PD-1/PD-L1 axis offer clinical benefits in solid tumors, including gastrointestinal malignancies.
• However, response rates to these therapies remain limited, affecting only 20-40% of patients.
• PD-L1 expression is a studied biomarker in gastrointestinal neoplasms, with established predictive value only in upper gastrointestinal cancers.

Purpose of the Study:

• To review technical aspects and challenges of PD-L1 immunohistochemical assays.
• To discuss the current clinical utility of PD-L1 as a biomarker.
• To outline studies and trials evaluating PD-L1's prognostic and predictive value in gastrointestinal cancers.

Main Methods:

• Literature review of studies and clinical trials.
• Analysis of technical aspects of PD-L1 immunohistochemical assays.
• Evaluation of PD-L1 expression patterns and biomarker utility.

Main Results:

• PD-L1 expression is extensively studied in gastrointestinal neoplasms.
• Predictive value of PD-L1 is currently established only for upper gastrointestinal adenocarcinomas and squamous cell carcinomas.
• Technical challenges and clinical practice roles of PD-L1 assays are discussed.

Conclusions:

• PD-L1 is a significant biomarker in gastrointestinal oncology, though its application is currently limited.
• Further research is needed to optimize PD-L1 assays and expand their use across gastrointestinal cancer types.
• Understanding PD-L1 expression is crucial for improving patient selection for immune-checkpoint inhibitor therapy.