Abstract CT009: IMvoke010: A phase III, double-blind randomized trial of atezolizumab (atezo) after definitive local therapy vs placebo in patients (pts) with high-risk locally advanced (LA) squamous cell carcinoma of the head and neck (SCCHN)

Abstract Background: Treatment (tx) for LA SCCHN includes a combination of surgery, radiation and/or chemotherapy followed by monitoring for local recurrence/distant metastases as standard of care. Given poor outcomes, there remains a clear unmet need in this pt population. IMvoke010 (NCT03452137) evaluated the efficacy and safety of atezo in pts with LA SCCHN who are at high-risk for disease progression following multi-modal definitive tx. Methods: Eligible pts with LA SCCHN (Stage IVa or IVb involving the oral cavity, larynx, hypopharynx, HPV negative oropharynx or Stage III HPV positive oropharynx [per AJCC 8th edition]) with no disease progression after multi-modal definitive tx were randomized (1:1) to receive atezo 1200 mg or placebo. Tx was given every 3 weeks for 1 year or until disease progression, unacceptable toxicity or consent withdrawal. Primary endpoint: investigator-assessed event-free survival (INV-EFS). Other key endpoints: overall survival (OS, secondary for efficacy) and safety. Results: A total of 406 pts were randomized to receive either atezo (n=203) or placebo (n=203). 156 (38.4%) pts underwent surgery as part of definitive tx. At clinical cutoff (27 September 2023), median follow-up was 46.5 months (mos). Median INV-EFS was 59.5 mos with atezo vs 52.7 mos with placebo (HR, 0.94; 95% CI, 0.70-1.26). INV-EFS results were generally consistent across all subgroups. OS showed no difference between arms for atezo vs placebo. Safety data are reported (Table). Conclusion: This study did not meet the primary endpoint of INV-EFS, a numerical improvement in INV-EFS was observed for atezo in pts with LA SCCHN, but this was not statistically significant. Atezo was generally well tolerated, and no new safety signals were identified. Table: Key efficacy and safety results Efficacy Atezo (n=203)* Placebo (n=203) Median INV-EFS, mos 59.5 52.7 HR (95% CI) 0.94 (0.70-1.26) P-value 0.6804† Median OS, mos NE NE HR (95% CI) 0.96 (0.68-1.36) Safety, n (%) Grade 3-4 AEs 55 (27.2) 43 (21.2) TRAEs Grade 3-4 20 (9.9) 12 (5.9) Grade 5 AEs 3 (1.5) 5 (2.5) SAEs 32 (15.8) 32 (15.8) AEs leading to tx discontinuation 18 (8.9) 9 (4.4) CI, confidence interval; HR, hazard ratio; *safety-evaluable pts (n=202); †α boundary: 0.0427 Citation Format: Deborah J. Wong, Jérôme Fayette, Maria Teixeira, Kumar Prabhash, Ricard Mesia, Andrzej Kawecki, Arunee Dechaphunkul, José Dinis, Ye Guo, Muneyuki Masuda, Ching-Yun Hsieh, Maria Grazia Ghi, Claudia Vaz de Melo Sette, Tao Jiang, Yibing Yan, Monika Kaul, Ritika Jagtiani, Christina Matheny, Vaikunth Cuchelkar, Robert Haddad. IMvoke010: A phase III, double-blind randomized trial of atezolizumab (atezo) after definitive local therapy vs placebo in patients (pts) with high-risk locally advanced (LA) squamous cell carcinoma of the head and neck (SCCHN) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT009.