The application and prospect of granzyme B-targeted PET imaging in cancer immunotherapy

In the context of cancer immunotherapy, assessing treatment response and predicting survival outcomes remain major challenges. Granzyme B (GZMB), released by cytotoxic T cells, represents the terminal effector event of activated antitumor immunity, thereby providing a robust rationale for GZMB-targeted positron emission tomography (GZMB PET) imaging as a noninvasive, real-time, and dynamic approach to monitoring immune activity within the tumor microenvironment. This review aims to 1) outline the molecular and immunological mechanisms of GZMB in antitumor immunity; 2) critically appraise the clinical value of GZMB PET beyond short-term response prediction; and 3) compare GZMB PET with existing imaging and biomarker‑based strategies, delineating its advantages, limitations, and translational prospects to inform future research and clinical practice.