Introduction
As the seventh most common tumor (1), head and neck cancer (HNC) consists of four major anatomical sites: the oral cavity, oropharynx, larynx, and nasopharynx (2), and almost 90% of it is head and neck squamous cell carcinoma (HNSCC)(3). HNSCC associates with the human papillomavirus (HPV) (HPV16/18) and tobacco (4), and the overall incidence rate of HNSCC in males is higher than in females (4). HPV-positive (HPV+) patients have a more favorable prognosis and more favorable responses to chemotherapy and radiotherapy than patients with HPV-negative (HPV-)(5). Conventional treatments for HNC involve surgery and chemoradiotherapy. Cetuximab, the antibody of epidermal growth factor receptor (EGFR), is also applied to the HNC treatment combined with cisplatin-based chemotherapy (6, 7). However, the efficiency of conventional treatments and cetuximab is limited(8). One of the first and most characterized immune evasion mechanisms is the PD pathway (9). Overwhelming evidence demonstrated that PD-1/PD-L1 immune inhibitors could reduce escaping tumor immune surveillance (T cell suppression)(10), enhance endogenous anti-tumor immunity (11). We first identified the suitable population for PD-1/PD-L1 inhibitors, compared the overall survival rate of the patients with different characteristics, analyzed the incidence of various adverse events in detail according to the classification, and included studies about PD-1/PD-L1 inhibitors with conventional therapy to guide clinical practice, which has not been studied(12-14).