Background and Aims: Atezolizumab plus bevacizumab (AtezoBev) is the standard of care for first-line treatment of unresectable HCC. No evidence exists as to its use in routine clinical practice in patients with impaired liver function.

Purpose: Atezolizumab + bevacizumab is the new standard of care for systemic treatment-naive, unresectable hepatocellular carcinoma (HCC). This exploratory study investigated on-treatment alpha-fetoprotein (AFP) response as a potential surrogate biomarker of prognosis for the combination therapy. Experimental Design: Data from Group A of the Phase Ib GO30140 study were used to identify the optimal time for AFP measurement and AFP cutoffs to differentiate patients by their best confirmed response per independent review facility-assessed Response Evaluation Criteria in Solid Tumors (IRF-RECIST) version 1.1: responders from non-responders and patients with disease control from primary progressors. We applied these cutoffs to independent data from the atezolizumab + bevacizumab arm of the Phase III IMbrave150 trial to distinguish patients based on (i) overall survival (OS) and progression-free survival (PFS) per IRF-RECIST 1.1; (ii) best confirmed response per IRF-RECIST 1.1. Results: We derived AFP cutoffs of {greater than or equal to}75% decrease and {less than or equal to}10% increase from baseline at 6 weeks to identify responders and those who had disease control, respectively. These cutoffs had high sensitivity and specificity in GO30140. In IMbrave150 patients, sensitivity was 0.59 and specificity was 0.86 for the {greater than or equal to}75% decrease AFP cutoff; the sensitivity was 0.77 and specificity was 0.44 for the {less than or equal to}10% increase AFP cutoff. Both AFP cutoffs were associated with longer OS and PFS, particularly in patients with hepatitis B virus etiology (HR <0.5; p <0.01). Conclusions: AFP response at 6 weeks after initiating treatment is a potential surrogate biomarker of prognosis for patients with HCC receiving atezolizumab + bevacizumab.

4073 Background: Atezo + bev has been approved in >60 countries for pts with unresectable HCC who have not received prior systemic therapy, based on IMbrave150 (NCT03434379; Finn RS NEJM 2020). Due to their poor prognosis and the hemodynamic changes from increased portal vein pressure, pts with main portal vein tumor thrombus are often excluded from pivotal HCC trials. Here, we report exploratory efficacy and safety results of pts with Vp4 (presence of a tumor thrombus in the main trunk and/or contralateral portal vein) using updated IMbrave150 data (Finn RS ASCO GI 2021). Methods: Pts were randomized 2:1 to atezo 1200 mg IV q3w + bev 15 mg/kg IV q3w or sor 400 mg bid until unacceptable toxicity or loss of clinical benefit per investigator. IMbrave150 enrolled 501 systemic treatment (tx)–naive unresectable HCC pts, ≥1 measurable untreated lesion (RECIST 1.1), Child-Pugh class A liver function and ECOG PS 0/1, including 73 (15%) Vp4 pts. This post hoc exploratory analysis was conducted with a median follow-up of 15.6 mo in ITT pts. Results: Of the Vp4 pts, 48 received atezo + bev and 25 received sor. Median OS (mOS) was 7.6 vs 5.5 mo (HR, 0.62; 95% CI: 0.34, 1.11) and median PFS (mPFS) per independent review facility (IRF)–assessed RECIST 1.1 was 5.4 vs 2.8 mo (HR, 0.62; 95% CI: 0.35, 1.09) with atezo + bev and sor, respectively. ORR per IRF RECIST 1.1 was 23% (11/47) with atezo + bev (2 [4%] pts had CR) vs 13% (3/23) with sor (1 [4%] pt had CR). All-grade variceal bleeding was higher with atezo + bev in Vp4 (13.6%) vs rest of ITT pts (2.5%). See table for further efficacy and safety data. Conclusions: The benefits of atezo + bev over sor in Vp4 pts are consistent with those in ITT pts across all efficacy endpoints, despite the expected disease-intrinsic increase in variceal bleeding in Vp4 vs rest of ITT pts. The overall positive benefit-risk profile supports the use of atezo + bev in pts with Vp4. Clinical trial information: NCT03434379. [Table: see text]

<b><i>Background:</i></b> Most phase 3 clinical trials of systemic therapy for first-line unresectable hepatocellular carcinoma (HCC) have failed, with the exception of SHARP, REFLECT, and IMbrave150. We conducted indirect comparisons of therapies evaluated for first-line HCC treatment. <b><i>Summary:</i></b> We conducted a systematic review and meta-analysis of treatments for adults with locally advanced or metastatic unresectable HCC and no prior systemic treatment, including atezolizu­mab plus bevacizumab, sorafenib, lenvatinib, nivolumab, selective internal radiotherapy (SIRT), transarterial chemoembolization, and placebo or best supportive care. Randomized controlled trials published from January 1, 2007, to March 12, 2020, were retrieved from MEDLINE and Embase. Qualitative assessment of heterogeneity evaluated study designs, populations, and outcomes. Indirect comparisons used generalized linear models with random effects within a Bayesian framework and informative priors. We calculated relative efficacy estimates with 95% credible intervals (CrIs) and Bayesian posterior probability estimates of atezolizumab-bevacizumab being superior to other treatments. Nine clinical studies with a total of 3,897 participants were identified from 8,783 records and used to build the all-trials evidence network. Indirect comparisons suggested an improved overall survival (OS) with atezolizumab-bevacizumab versus lenvatinib (odds ratio, 0.63 [95% CrI 0.39–1.04]; with 97% Bayesian posterior probability of being superior), nivolumab (0.68 [95% CrI 0.41–1.14]; 94%), sorafenib (0.59 [95% CrI 0.39–0.87]; 99%), SIRT (0.51 [95% CrI 0.32–0.82]; 100%), or placebo/best supportive care (0.40 [95% CrI 0.25–0.64]; 100%). <b><i>Key Messages:</i></b> Within the context of indirect comparisons, analyses of OS favored atezolizumab-bevacizumab versus other treatment options for patients with locally advanced or metastatic unresectable HCC.

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