The final articles included in the review, along with their respective data.
| Author and year | Country | Databases searched | No. of OSCC studies included | Parameters | Main findings | Methodology |
|---|---|---|---|---|---|---|
| He et al., 2020 [12] | China | PubMed, Web of Science, EMBASE, Cochrane Library, and CNKI | 23 | PD-L1 and clinicopathological features | High PD-L1 linked to adverse clinicopathological traits; no impact on overall survival (OS). | PD-L1 expression was detected using immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded (FFPE) tissue, evaluated in tumor cells. |
| Yang et al., 2018 [13] | China | PubMed, Embase, Web of Science, Cochrane Library, and Scopus | 9 | PD-L1 and prognosis | Positive PD-L1 may predict better progression-free survival (PFS) in advanced HNSCC; interaction with CD8+ tumor infiltrating lymphocytes (TILs) noted. | PD-L1 was detected via IHC on FFPE tissue sections, with expression assessed in both tumor and immune cells. |
| Tang et al., 2019 [14] | China | PubMed, Embase, and Cochrane | 9 | PD-L1, clinicopathological features; and survival | PD-L1 overexpression is associated with females; disease-free survival (DFS) significance only in the oropharyngeal squamous cell carcinoma (OPSCC) subgroup. | PD-L1 was assessed via IHC on FFPE tissue sections, with expression evaluated in tumor cells. |
| Lenouvel et al., 2020 [15] | Spain | PubMed, Embase, Web of Science, and Scopus | 26 | PD-L1, clinicopathological features, and survival | PD-L1 correlated with poor disease-specific survival (DSS)/DFS; it was higher in females, non-smokers, and advanced tumors. | PD-L1 expression was measured using IHC with specific antibody clones on FFPE samples, evaluated in both tumor and immune cells. |
| Patel et al., 2020 [16] | South Carolina | PubMed (NLM NIH), Scopus (Elsevier), Embase (Elsevier), Web of Science (Clarivate), and Cochrane Library (Wiley) | 6 | PD-L1, OS, and HPV | PD-L1 expression linked to better response and OS; HPV status had no survival impact. | PD-L1 detection was performed using IHC on FFPE tissue sections, with evaluation in tumor cells. |
| Troiano et al., 2019 [17] | Italy | PubMed, Scopus, Web of Science | 11 | PD-L1 and OS | High PD-L1 is not linked to poor prognosis; findings varied across studies. | IHC was used on FFPE specimens to detect PD-L1 expression, evaluated in tumor cells. |
Data extracted from the systematic reviews conducted on PD-L1 receptors and OSCC. OSCC: oral squamous cell carcinoma; PD-L1: programmed death-ligand 1; HNSCC: head and neck squamous cell carcinoma; HPV: human papilloma virus.