PD-L1 expression in anogenital and oropharyngeal squamous cell carcinomas associated with different clinicopathological features, HPV status and prognosis: a meta-analysis

Background: Little research has been done on clinicopathological characteristics and human papillomavirus (HPV) status of anogenital and oropharyngeal squamous cell carcinomas (SCC) with a strong expression of programmed death ligand 1 (PD-L1) in tumor cells. Therefore, we conducted this meta-analysis. Methods: We performed a comprehensive research in PubMed, Embase and Cochrane databases up to 30 September 2020. The effect size was hazard ratio (HR) with 95% confidence interval (CI) for overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS). The pooled odds ratio (OR) with 95% CI were used to assess the association between PD-L1 expression and clinicopathological features along with HPV status. Results: A total of 2003 cases (944 anogenital and 1059 oropharynx SCC patients) were included. High PD-L1 expression in anogenital SCC cases were associated with advanced age (OR = 1.63, 95% CI: 1.04–2.58) and HPV negativity (OR = 0.47, 95% CI: 0.31–0.71). Besides, PD-L1 positive anogenital SCC cases held a significantly declined OS (HR = 2.18, 95% CI: 1.37–3.47) and CSS (HR = 2.45, 95% CI: 1.30–4.65). For oropharynx SCC, PD-L1 was more frequent in younger and HPV positive patients (OR = 0.60, 95% CI: 0.37–0.98; OR = 3.01, 95% CI: 1.78–5.09) and PD-L1 expression was relevant to better OS and DFS (HR = 0.76, 95% CI: 0.60–0.97; HR = 0.50, 95% CI: 0.33–0.75). Conclusions: The meta-analysis demonstrated that in anogenital SCC, PD-L1 positivity had to do with a worse outcome, which might attribute to advanced age, higher tumor grade, lymph node metastasis and HPV negativity, while in oropharynx cancer, PD-L1 expression was related to better prognosis for the reason that PD-L1 was less frequent in the aged and negative HPV status.