Real-world (RW) experience with atezolizumab + bevacizumab (A+B) for the treatment of unresectable HCC (uHCC): A multicenter study.

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537 Background: A+B is the preferred first-line (1L) standard of care for uHCC, with emerging RW evidence supporting its use in a broad patient (pt) cohort. We evaluated pt characteristics, clinical and treatment outcomes in pts treated at five U.S. institutions: Mayo Clinic, Houston Methodist, Moffitt Cancer Center, Mays Cancer Center, and University of Arizona. Methods: This is a retrospective study of uHCC pts who initiated A+B after January 1, 2019. De-identified pt data were extracted by treating oncologists. Overall survival (OS) and real-world progression-free survival (rwPFS) were assessed using Kaplan-Meier methods for all pts and for a “trial-like” subgroup with characteristics similar to those in the IMbrave150 trial (ECOG performance status [PS] 0-1, Child-Pugh [CP] class A, albumin-bilirubin [ALBI] grade 1-2). HCC-related hospitalizations were evaluated within 1 year of A+B initiation. Results: A total of 300 eligible pts were treated with 1L A+B (median age 68 years, 79% male, 79% White, 82% BCLC C, 44% viral etiology,12% ECOG PS >1). Liver function was CP A in 73% (36% A5, 31% A6, 6% not reported), CP B in 26% pts (15% B7, 7% B8, 5% B9), and CP C in 2 (<1%) pts. Compared with CP A, more CP B pts had characteristics of compromised liver function (CP A vs B: cirrhosis: 61% vs 91%; ascites: 7% vs 46%; encephalopathy: 4% vs 17%; esophageal varices: 14% vs 32%), bile duct invasion (2% vs 11%), and ECOG PS>1 (8% vs 22%), all Ps<0.001. Over a median follow-up of 8.7 mos, 244 (81%) pts discontinued A+B, primarily due to disease progression. Toxicity-related treatment discontinuation and hospitalizations due to treatment-related adverse events (TRAE) were similar between the two groups (Table). Median OS (mOS) was 14.4 mos (95% CI: 12.3, 18.2) and median rwPFS was 6.8 mos (95% CI: 5.8, 8.4). In the trial-like subgroup (n=194), mOS was 19.5 mos (95%CI: 14.6, 24.7) and median rwPFS was 8.8 mos (95% CI: 7.6, 12.1). In the CP B subgroup, mOS was 5.6 mos (95% CI: 4.6, 11.3) and median rwPFS was 3.1 mos (95% CI: 2.4, 5.8). Conclusions: This study demonstrates the RW outcomes of 1L A+B in a diverse pt cohort. Results from the “trial-like” pts further confirm the reproducible efficacy of A+B in clinical practice. Although pts with CP-B had higher hospitalization rates due to disease progression or symptoms, consistent with their underlying liver complications, they had similar rates of toxicity-related treatment discontinuation and TRAE-related hospitalizations compared to CP-A. Further characterization of safety for A+B in CP B pts within a prospective, controlled trial is warranted. N (%) CP A (n=219) CP B (n=79) Treatment discontinuation* 167 (76) 75 (95) Atezolizumab-related toxicity 20 (12) 13 (17) Bevacizumab-related toxicity 26 (16) 16 (21) Hospitalization* 87 (40) 58 (73) Symptom-related 42 (48) 35 (60) Progression 8 (9) 11 (19) TRAE 7 (8) 6 (10) *P-value comparing CP A vs CP B <0.001.