PD-1/PD-L1 的上调使癌细胞能够通过功能性失活 T 细胞免疫监视来逃避宿主免疫系统。临床封锁策略导致晚期癌症患者的患病率增加。然而，许多癌症患者对当前的免疫治疗策略反应有限或没有反应。因此，如何提高免疫治疗的敏感性成为众多学者关注的焦点。放疗在肿瘤微环境中发挥T细胞募集作用，增加CD4  和CD8  T细胞，增加PD-L1表达，导致放疗和PD-L1阻断协同增强抗肿瘤作用。放疗会引起肿瘤代谢尤其是糖代谢的变化。肿瘤糖酵解和肿瘤免疫逃避是相互依赖的，糖酵解活性增强肿瘤细胞上PD-L1的表达，从而促进抗PD-L1免疫治疗反应。因此，放疗影响肿瘤免疫的机制可能部分是通过干预肿瘤糖代谢来实现的。此外，一些作者发现2'-脱氧-2'-[18F]氟-D-葡萄糖(18F-FDG)的摄取与PD-1/PD-L1表达相关。正电子发射断层扫描/计算机断层扫描（PET/CT）是一种非侵入性的PD-1/PD-L1表达检测方法，与免疫组化（IHC）相比具有多种潜在优势，PET/CT可以动态反映PD-1的表达情况/PD-L1 在肿瘤内部并进一步指导临床治疗。© 2023。作者获得日本放射线学会独家许可。

Upregulation of PD-1/PD-L1 allows cancer cells to escape from host immune systems by functionally inactivating T-cell immune surveillance. Clinical blockade strategies have resulted in an increased prevalence of patients with late-stage cancers. However, many cancer patients had limited or no response to current immunotherapeutic strategies. Therefore, how to improve the sensitivity of immunotherapy has become the focus of attention of many scholars. Radiotherapy plays a role in the recruitment of T cells in the tumor microenvironment, increases CD4 + and CD8 + T cells, and increases PD-L1 expression, resulting in the synergistically enhanced antitumor effect of irradiation and PD-L1 blockade. Radiotherapy can cause changes in tumor metabolism, especially glucose metabolism. Tumor glycolysis and tumor immune evasion are interdependent, glycolytic activity enhances PD-L1 expression on tumor cells and thus promotes anti-PD-L1 immunotherapy response. Therefore, the mechanism of radiotherapy affecting tumor immunity may be partly through intervention of tumor glucose metabolism. Furthermore, some authors had found that the uptake of 2'-deoxy-2'-[18F]fluoro-D-glucose(18F-FDG) was correlated with PD-1/PD-L1 expression. Positron emission tomography/computed tomography (PET/CT) is a non-invasive detection method for PD-1/PD-L1 expression and has several potential advantages over immunohistochemical (IHC), PET/CT can dynamically reflect the expression of PD-1/PD-L1 inside the tumor and further guide clinical treatment.© 2023. The Author(s) under exclusive licence to Japan Radiological Society.