Phase I study investigating definitive radioimmunotherapy (RIT) with nivolumab and ipilimumab for the treatment of locally advanced (LA) squamous cell carcinoma of the head and neck (SCCHN) The primary endpoint was safety of definitive RIT . Secondary endpoints included progression-free survival (PFS) and overall survival . 5 individuals developed in-field soft tissue ulceration during consolidation immunotherapy, resulting in one fatality . The 3-year PFS and OS rates were 74% (95% CI 58% to 94%), respectively. PD-L1 combined positive score (CPS) did not correlate with death or disease progression .