Abstract CT003: IMbrave050: Phase 3 study of adjuvant atezolizumab + bevacizumab versus active surveillance in patients with hepatocellular carcinoma (HCC) at high risk of disease recurrence following resection or ablation

Abstract Background: The risk of HCC recurrence after liver resection or ablation with curative intent is 70-80% within 5 years, indicating an unmet need for effective adjuvant therapies. Atezolizumab (atezo) with bevacizumab (bev) is the standard of care for unresectable HCC based on the IMbrave150 study, which demonstrated statistically significant and clinically meaningful improvements in overall survival (OS), progression-free survival, and objective response rate versus sorafenib (Finn NEJM 2020, Cheng J Hepatol 2022). On the basis of the antitumor activity of atezo + bev and its capacity to positively modulate the tumor microenvironment, IMbrave050 was designed to evaluate the efficacy of adjuvant atezo + bev in delaying or preventing recurrence in patients (pts) with high-risk HCC. Methods: IMbrave050 (NCT04102098) enrolled pts with HCC at high risk of recurrence following resection or ablation. High-risk criteria were based on tumor burden (tumor size and number), vascular invasion, and tumor differentiation. Pts were randomized to Arm A (atezo + bev) or Arm B (active surveillance). Stratification factors included geographic region (Asia-Pacific excluding Japan vs rest of world) and a composite factor encompassing the number of high-risk features, curative procedure, and use of optional adjuvant TACE (allowed for one cycle following resection). Pts in Arm A received atezo 1200 mg + bev 15 mg/kg IV q3w for a period of one year or 17 cycles. Pts in Arm B underwent active surveillance for one year and were eligible to crossover to atezo + bev following independent review facility (IRF) confirmation of recurrence. The primary endpoint was IRF-assessed recurrence-free survival (RFS). Secondary efficacy endpoints included OS; investigator-assessed (INV) RFS; RFS and OS according to PD-L1 status; and time to extrahepatic spread and/or macrovascular invasion. Results: The ITT population included 334 pts each in Arms A and B. Baseline demographics were well balanced between arms. At interim analysis, with a median follow-up of 17.4 mo (cut off date: Oct 21, 2022), the primary endpoint was met with an IRF-RFS HR of 0.72 (95% CI, 0.56, 0.93; P=0.0120), and results were generally consistent across clinical subgroups. INV-RFS was similar (HR, 0.70; 95% CI, 0.54, 0.91). The safety of atezo + bev was generally manageable and consistent with the well-established safety profile of each therapeutic agent and with the underlying disease. Conclusions: Atezo + bev is the first adjuvant regimen to demonstrate a statistically significant and clinically meaningful improvement in RFS vs active surveillance in pts at high risk of disease recurrence following resection or ablation. The benefit:risk profile of atezo + bev favors the use of this regimen as an adjuvant therapy and has potential to set a new standard of care in adjuvant HCC. Citation Format: Pierce Chow, Minshan Chen, Ann-Lii Cheng, Ahmed O. Kaseb, Masatoshi Kudo, Han Chu Lee, Adam Yopp, Jian Zhou, Lu Wang, Xiaoyu Wen, Jeong Heo, Won Young Tak, Shinichiro Nakamura, Kazushi Numata, Thomas Uguen, David Hsiehchen, Edward Cha, Stephen P. Hack, Qinshu Lian, Jessica Spahn, Chun Wu, Shukui Qin. IMbrave050: Phase 3 study of adjuvant atezolizumab + bevacizumab versus active surveillance in patients with hepatocellular carcinoma (HCC) at high risk of disease recurrence following resection or ablation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT003.