Pembrolizumab versus cetuximab concurrent with radiotherapy in patients with locally advanced squamous cell carcinoma of head and neck unfit for cisplatin (GORTEC 2015-01 PembroRad): a multicenter, randomized, phase II trial

Background To evaluate potential synergistic effect of pembrolizumab with radiotherapy (RT) compared with a standard-of-care (SOC) cetuximab–RT in patients with locally advanced-squamous cell carcinoma of head and neck (LA-SCCHN). Patients and methods Patients with nonoperated stage III-IV SCC of oral cavity, oropharynx, hypopharynx, and larynx and unfit for receiving high-dose cisplatin were enrolled. Patients received once-daily RT up to 69.96 Gy in 33 fractions with weekly cetuximab (cetuximab–RT arm) or 200 mg Q3W pembrolizumab during RT (pembrolizumab–RT arm). The primary endpoint was locoregional control (LRC) rate 15 months after RT. To detect a difference between arms of 60%-80% in 15-month LRC, inclusion of 66 patients per arm was required to achieve a power of at least 0.85 at two-sided significance level of 0.20. Results Between May 2016 and October 2017, 133 patients were randomized to cetuximab–RT (n = 66) and pembrolizumab–RT (n = 67). Two patients (one in each arm) were not included in the analysis (a consent withdrawal and a progression before treatment start). The median age was 65 years (interquartile range 60-70 years), 92% were smokers, 60% were oropharynx (46% of oropharynx with p16+) and 75% were stage IV. Median follow-up was 25 months in both arms. The 15-month LRC rate was 59% with cetuximab–RT and 60% with pembrolizumab–RT ]odds ratio 1.05, 95% confidence interval (CI) 0.43-2.59; P = 0.91]. There was no significant difference between arms for progression-free survival (hazard ratio 0.85, 95% CI 0.55-1.32; P = 0.47) and for overall survival (hazard ratio 0.83, 95% CI 0.49-1.40; P = 0.49). Toxicity was lower in the pembrolizumab–RT arm than in the cetuximab–RT arm: 74% versus 92% patients with at least one grade ≥3 adverse events (P = 0.006), mainly due to mucositis, radiodermatitis, and rash. Conclusion Compared with the SOC cetuximab–RT, pembrolizumab concomitant with RT did not improve the tumor control and survival but appeared less toxic in unfit patients with LA-SCCHN.