The character of the tumor microenvironment is a relevant prognostic and predictive biomarker across a wide range of malignancies. The composition, density, and functional capacity of tumor-infiltrating immune cells are especially crucial for selecting suitable immunotherapy. Head and neck squamous cell carcinomas are considered immunologically hot tumors, with high numbers of tumor-infiltrating effector and regulatory T cells. Higher T cell counts, along with a better prognosis, were observed in patients with head and neck squamous cell carcinomas associated with human papillomavirus infection. The immune profile of smoking-associated tumors was more variable, with higher numbers of suppressive myeloid cells and a substantial variability in T cell numbers between the patients. Nevertheless, the high density of cytotoxic T cells was a stronger prognostic factor for head and neck squamous cell carcinoma patients than HPV status alone. Thus, prognostic markers based on knowledge of the tumor microenvironment and tumor-infiltrating immune cells could significantly improve patient stratification for immunotherapeutic and de-escalation treatment protocols.
Keywords: HNSCC; HPV; head and neck squamous cell carcinoma; tumor microenvironment.