Putting the Microenvironment into the Immunotherapy Companion Diagnostic

Area of Science:

• Oncology
• Immunotherapy
• Cancer Diagnostics

Background:

• Advanced gastric cancer (AGC) remains a significant health challenge.
• Immunotherapy, particularly targeting the PD-1/PD-L1 pathway, has emerged as a promising treatment modality for AGC.
• Accurate predictive biomarkers are crucial for optimizing immunotherapy selection and patient outcomes.

Purpose of the Study:

• To investigate the association between programmed cell death-ligand 1 (PD-L1) expression and immunotherapy efficacy in advanced gastric cancer.
• To compare the predictive value of PD-L1 expression in tumor cells (TC%) versus immune cells using the combined positive score (CPS).
• To assess the clinical utility of PD-L1 expression in the tumor microenvironment for companion diagnostics.

Main Methods:

• A post hoc analysis was conducted on data from patients with advanced gastric cancer treated with immunotherapy.
• PD-L1 expression was evaluated using immunohistochemistry.
• Combined positive score (CPS) and tumor cell (TC%) scoring methods were employed to quantify PD-L1 expression.
• Statistical analyses were performed to determine the association between PD-L1 expression levels and treatment response.

Main Results:

• A stronger association was observed between PD-L1 expression, as measured by CPS, and immunotherapy efficacy compared to TC% scoring.
• The CPS metric, which incorporates PD-L1 expression on both tumor and immune cells, demonstrated superior predictive value.
• These findings suggest that PD-L1 expression within the tumor microenvironment, particularly on immune cells, is a critical determinant of treatment response.

Conclusions:

• Combined positive score (CPS) is a more robust biomarker than tumor cell (TC%) scoring for predicting immunotherapy efficacy in advanced gastric cancer.
• The expression of PD-L1 in immune cells within the tumor microenvironment significantly enhances the predictive value of companion diagnostic tests.
• Optimizing companion diagnostics by considering immune cell PD-L1 expression can improve patient selection for immunotherapy and treatment outcomes.