Re-irradiation for oligoprogression under Nivolumab in recurrent head and neck squamous cell carcinoma: A case report.

Immune checkpoint inhibitors (ICIs) represent a recently introduced class of agents active in head and neck squamous cell carcinoma (HNSCC). For a subgroup of patients with recurrent or metastatic disease, long-term benefit can be achieved: maintaining a sustained response to immunotherapy is therefore a critical factor for its efficacy at an individual level. In analogy to targeted agents, a limited pattern of progression, or "oligoprogression", can occur. For locally recurrent HNSCC, the potential biologic interplay between the efficacy of ICIs and the design of radiation fields chosen for primary treatment is currently unknown. Here, we report on a patient who presented two subsequent oligoprogressions successfully treated with re-irradiation without interrupting Nivolumab. Both oligoprogressive lesions developed in previously unirradiated areas. We hypothesize the existence of a synergistic effect with optimal spatial cooperation between ICIs and re-irradiation for oligoprogressive disease under immunotherapy.