Background & aims: Validated surrogate endpoints for overall survival (OS) are important for expediting the clinical study and drug-development processes. Herein, we aimed to validate objective response as an independent predictor of OS in individuals with unresectable hepatocellular carcinoma (HCC) receiving systemic anti-angiogenic therapy.

Methods: We investigated the association between objective response (investigator-assessed mRECIST, independent radiologic review [IRR] mRECIST and RECIST v1.1) and OS in REFLECT, a phase III study of lenvatinib vs. sorafenib. We conducted landmark analyses (Simon-Makuch) of OS by objective response at 2, 4, and 6 months after randomization.

Results: Median OS was 21.6 months (95% CI 18.6-24.5) for responders (investigator-assessed mRECIST) vs. 11.9 months (95% CI 10.7-12.8) for non-responders (hazard ratio [HR] 0.61; 95% CI 0.49-0.76; p <0.001). Objective response by IRR per mRECIST and RECIST v1.1 supported the association with OS (HR 0.61; 95% CI 0.51-0.72; p <0.001 and HR 0.50; 95% CI 0.39-0.65; p <0.001, respectively). OS was significantly prolonged for responders vs. non-responders (investigator-assessed mRECIST) at the 2-month (HR 0.61; 95% CI 0.49-0.76; p <0.001), 4-month (HR 0.63; 95% CI 0.51-0.80; p <0.001), and 6-month (HR 0.68; 95% CI 0.54-0.86; p <0.001) landmarks. Results were similar when assessed by IRR, with both mRECIST and RECIST v1.1. An exploratory multivariate Cox regression analysis identified objective response by investigator-assessed mRECIST (HR 0.55; 95% CI 0.44-0.68; p <0.0001) and IRR-assessed RECIST v1.1 (HR 0.49; 95% CI, 0.38-0.64; p <0.0001) as independent predictors of OS in individuals with unresectable HCC.

Conclusions: Objective response was an independent predictor of OS in individuals with unresectable HCC in REFLECT; additional studies are needed to confirm surrogacy. Participants achieving a complete or partial response by mRECIST or RECIST v1.1 had significantly longer survival vs. those with stable/progressive/non-evaluable disease.

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© 2022 The Authors. Published by Elsevier B.V. on behalf of European Association for the Study of the Liver. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). J. Hepatol. 2023, 78, 133–141

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