The promise of immunotherapy in head and neck squamous cell carcinoma: combinatorial immunotherapy approaches

The immune system plays a fundamental role in preventing cancer development by recognising and eliminating tumour cells. The recent success in the field of immunotherapy has confirmed the potential to exploit the immune response as a cancer treatment. Head and neck squamous cell carcinoma ( HNSCC) is a malignancy characterized by dismal prognosis and high mortality rate; low survival outcomes in combination with significant toxicity of current treatment strategies highlight the necessity for novel therapeutic modalities. HNSCC is a favourable disease for immunotherapy, as immune escape plays a key role in tumour initiation and progression. T-cell checkpoint inhibitors targeting programmed cell death protein-1 have emerged as novel immunotherapy agents showing remarkable efficacy in HNSCC. However, only a minority of patients derive benefit for singleagent immunotherapies. In this regard, combinatorial immunotherapy approaches represent an alternative strategy that might increase the number of patients who respond to immunotherapy. Focusing on HNSCC, this review will summarise novel combinations of immune checkpoint blockade with other immunotherapy treatment modalities.