Immuno-oncology in head and neck squamous cell cancers: News from clinical trials, emerging predictive factors and unmet needs.

According to the new determinants of cancer immunity, head and neck squamous cell cancer (HNSCC) has to be considered as an immunogenic tumor for the relatively high number of somatic mutations giving rise to neoantigens recognized by T cell. HNSCC develop at a significant rate despite the antitumoral immune response indicating the existence of effective escape mechanisms. The lack of antigen presentation or co-stimulatory molecules required and immunosuppressive phenomena established by the tumor or the host microenvironment impair immune-mediated recognition and cancer control. Echoing the success in melanoma and NSCLC, strategies aimed to reverse this process and enhance the antitumor immunity are rapidly developing in HNSCC, as monotherapies, multidrug immunotherapies or associations with well-recognized treatments, like radiation and systemic therapies. According to the first published data, immunotherapy has shown promising results in the management of recurrent and metastatic (r/m) HNSCC. Anti-PD-1 blockers have been recently approved by US and EU regulatory agencies in this setting. The encouraging results in r/m HNSCC prompted the incorporation of this approach also in the treatment of locally advanced disease. However, the strategies for the rational and evidence-based combinations to maximize clinical benefit are only starting to emerge. In this view, knowing in depth the specific properties of HNSCC and the underlying immunological conditions of the bearing hosts is an essential step. The role of immune system in the development and the management of HNSCC, the main mechanisms of tumor escape and the most recent results from clinical trials will be discussed herein.