Safety of nivolumab and ipilimumab in combination with radiotherapy in patients with locally advanced squamous cell carcinoma of the head and neck (LA SCCHN).

Abstract

6070 Background: Standard cisplatin-based chemoradiotherapy for LA SCCHN is associated with toxicity and less than desirable survival in high-risk patients (pts). The combination of the anti-PD1 antibody nivolumab (nivo) and the anti-CTLA-4 antibody ipilimumab (ipi) has been effective in melanoma and renal cell carcinoma and is under investigation in other solid tumors including SCCHN. Combining RT and immunotherapy (IO) has a strong preclinical rationale and is being evaluated in the clinic. This pilot trial combines IO and RT to build upon these observations. Methods: We enrolled previously untreated high-risk pts with AJCC 7th edition stage IVA-IVB SCCHN of the oral cavity, oropharynx (OP), hypopharynx, larynx. HPV+ OP tumors were T4, or N2c or N3 by AJCC 7th edition criteria. Nivo 3 mg/kg was administered every 2 weeks IV x 17 doses and ipi 1 mg/kg every 6 weeks x 6 doses beginning 2 weeks before IMRT 2 Gy/fraction/day given to total dose 70 Gy. The primary safety endpoint was acute in-field toxicity. Exploratory correlative studies include tumor PD-L1 expression, tumor immune bias, and exosome quantity and composition. The total sample size is 24 pts with 12 enrolled in the first stage and 12 in the expansion cohort. Results: A planned safety analysis was performed in the first 12 pts (8 OP; 1 hypopharynx; 3 larynx). No acute grade (G) 4 or dose-limiting toxicities were seen. Acute G 3 in-field toxicity occurred during RT in 50% of pts: dysphagia (4 pts), mucositis (3), odynophagia (2), hoarseness (1), dermatitis (1). 50% of pts had immune-related toxicity at any time. 3 pts discontinued treatment at > 3 months post RT: 1 for an immune-related cause (G 3 colitis that resolved with steroids), and 2 for non-immune-related causes (1 G 5 bleeding due to carotid rupture secondary to an in-field ulcer at 4 months post RT in a pt with complete response and 1 G 3 OP ulcer resolving with hyperbaric oxygen). 1 pt with a laryngeal primary developed a solitary lung metastasis vs new primary 6 months post RT. 10 of 12 pts are alive with no evidence of disease (follow up 7.2-18.4 months). Conclusions: Preliminary results with this non-platinum-containing RT plus IO regimen are encouraging. Longer follow-up is needed for assessment of late effects and efficacy. Enrollment is ongoing in the expansion cohort. This study is supported by BMS. Clinical trial information: NCT03162731.