Moving towards the Future of Radio-Immunotherapy: Could We “Tailor” the Abscopal Effect on Head and Neck Cancer Patients?

The abscopal effect (AbE) is defined as radiation-induced shrinkage of distant, non-treated, neoplastic lesions and it is considered the best clinical picture of the efficient immune stimulation by irradiation. The first report about abscopal tumor regression upon radiotherapy dates back to the beginning of the 20th century. The growing preclinical and clinical synergism between radiation and immunotherapy gave birth the purpose to more easily reproduce the abscopal effect, nevertheless, it is still rare in clinical practice. In this review we summarize immunological modulation of radiotherapy, focusing on the well-balanced equilibrium of tumor microenvironment and how radio-immunotherapy combinations can perturb it, with particular attention on head and neck squamous cell cancer. Finally, we investigate future perspectives, with the aim to “tailor” the abscopal effect to the patient.