对于头颈部鳞状细胞癌（HNSCC）患者的激进治疗的失败或成功与许多已知和未知的因素相关联，因此正在寻找进一步的预后标记，以帮助优化治疗策略，并改善治疗效果。评估编程细胞死亡配体1（PD-L1）在免疫或肿瘤细胞上的表达，包括其在两种细胞类型上的复合表达与总生存期（OS）或特定生存期的关联。系统地搜索MEDLINE，Embase，PQSciTech和HCAPlus数据库，寻找针对疾病治愈阶段中HNSCC患者PD-L1表达预后作用的队列研究。搜索结果生成了从2010年1月1日至2023年1月6日期间的出版物。在3825篇发现的出版物中，总共有17篇符合本系统性综述和Meta分析的纳入标准的英文队列研究。符合资格的研究报告了PD-L1表达水平与OS和任意特定生存期的关联的调整危险比（aHR）和95％置信区间（CI）。 本研究的主要目的是调查免疫或肿瘤细胞上的PD-L1表达与OS之间的关联。在17个队列研究中，通过对3190名HNSCC患者的PD-L1表达与生存的关联进行分析，发现高PD-L1表达与免疫细胞对OS有有利的关联（合并aHR为0.39，95％CI为0.25-0.59）。免疫和肿瘤细胞上的复合PD-L1表达及肿瘤细胞上单独表达的PD-L1均未与OS有关联。在免疫细胞上高水平的PD-L1表达与有利的特定生存相关联（合并aHR为0.52；95％CI为0.38-0.72）。肿瘤部位或主要治疗方法（即手术 vs 放疗或放疗化疗）与PD-L1表达与OS之间没有相互作用。 研究结果表明，对于HNSCC患者，免疫细胞上的PD-L1表达可能作为一种新的预后生物标记物。但是，鉴于在这个主题上进行并发布的研究数量有限，未来可能需要进行其他研究来验证其潜在的作用。

The failure or success of radical treatment in patients with head and neck squamous cell carcinoma (HNSCC) is associated with many known and unknown factors; hence, there is a search for further prognostic markers to help optimize therapeutic strategy and improve treatment outcomes.To assess the association of programmed cell death ligand 1 (PD-L1) expression on immune or tumor cells, including its composite expression on both cell types, with overall survival (OS) or specific survival.MEDLINE, Embase, PQSciTech, and HCAPlus databases were systematically searched for cohort studies focused on the prognostic role of PD-L1 expression in patients with HNSCC in curative stages of the disease. Search results generated publications from January 1, 2010, to January 6, 2023.Of 3825 publications identified, a total of 17 cohort studies in the English language met inclusion criteria of this systematic review and meta-analysis. Eligible studies reported adjusted hazard ratios (aHRs) with 95% CIs for the association of PD-L1 expression levels with OS and arbitrary specific survival.Data from studies were extracted independently by 2 researchers strictly adhering to the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guidelines and recommendations. The risk of bias was assessed using the Quality in Prognosis Studies tool and Newcastle-Ottawa Scale. Pooled effect estimates were obtained using a random-effect or fixed-effect model based on homogeneity of studies.The primary outcome was to investigate whether there was an association between PD-L1 expression on immune or tumor cells and OS.In 17 cohort studies of the association of PD-L1 expression with survival in 3190 patients with HNSCC, high PD-L1 expression on immune cells was associated with a favorable OS (pooled aHR, 0.39; 95% CI, 0.25-0.59). There was no association between composite PD-L1 expression on immune and tumor cells and OS (pooled aHR, 0.79; 95% CI, 0.55-1.14) or between PD-L1 expressed only on tumor cells and OS (pooled aHR, 1.22; 95% CI, 0.87-1.70). A high level of PD-L1 expression on immune cells was associated with favorable specific survival (pooled aHR, 0.52; 95% CI, 0.38-0.72). There were no interactions between tumor location or type of primary treatment (ie, surgery vs radiotherapy or radiochemotherapy) and the association between PD-L1 expression and OS.This study's findings suggest that PD-L1 expression on immune cells may serve as a new prognostic biomarker in patients with HNSCC. However, future studies may be warranted to verify this potential role given the limited number of studies on this topic conducted and published to date.