672P Nivolumab (Nivo) and ipilimumab (Ipi) combined with radiotherapy (RT) in patients (pts) with locally advanced squamous cell carcinoma of the head and neck (LA SCCHN): Updated results on efficacy and correlative analysis

Abstract

Immune checkpoint inhibitors are standard of care in recurrent/metastatic SCCHN. We evaluated concurrent radioimmunotherapy (RIT) with Nivo and Ipi in the definitive setting for patients with high-risk LA SCCHN. Pts with newly diagnosed, AJCC 7th edition stage IVA-IVB SCCHN of the oropharynx (OP; OP HPV+ were T4, N2c or N3), hypopharynx, and larynx that were eligible for chemotherapy received Nivo (3 mg/kg Q2 weeks x 17) and Ipi (1 mg/kg Q6 weeks x 6) starting 2 weeks prior to IMRT (2 Gy/fraction/day to a total of 70 Gy). The primary endpoint was safety of RIT. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). Exploratory endpoints included the association of baseline PD-L1 expression as well as on-treatment changes in immune bias with treatment outcomes. 24 pts (16 OP of whom 14 HPV+) were enrolled and followed for a median of 36.1 months. At data cutoff, 7 PFS events were noted, including 5 distant recurrences, 1 regional recurrence and 1 death without evidence of disease progression. The 3-year PFS and OS rates were 74% (95% CI, 58%-94%) and 96% (95% CI, 88%-100%), respectively. PD-L1 CPS did not correlate with death or disease progression. Among peripheral blood cytokines, increased MCSF levels were associated with prolonged PFS at several timepoints (baseline [p=0.038], post-induction [p=0.031], and at the end of RT [p=0.023]); interval increase in IFNg inducing factor (IL18) within the induction phase was also associated with prolonged PFS (p=0.031), as were post-induction IFNg levels (p=0.041). 5 pts developed in-field ulcerations during consolidation immunotherapy (median time to detection was 3 months post RT completion). PD-L1 CPS did not correlate with ulceration. Interestingly, interval increase in IL9, IL4, IL12, and IL17a during concurrent RIT appeared to protect from in-field ulcerations. Definitive RIT has sufficient clinical activity to support further development. Cytokine profiles appear able to predict treatment failure, as well as in-field ulcerations early during treatment.