Impact of radiological response and pattern of progression in patients with hepatocellular carcinoma treated by atezolizumab- bevacizumab

Background & Aims: We aim to assess the role of radiological response to atezolizumab-bevacizumab (AtezoBev) in patients with hepatocellular carcinoma (HCC) to predict overall survival (OS).Approach & Results: We retrospectively included HCC patients treated by AtezoBev in two tertiary centers. A retrospective blinded analysis was performed by two radiologists to assess RECIST1.1 and mRECIST criteria at 12 weeks. Imaging response and treatment decision in the multidisciplinary tumor board (MTB) at 12 weeks were registered. Among 125 patients, 9.6% and 20.8% had response, 39.2% and 35.2% stable disease and 51.2% and 44% progression, according to RECIST 1.1 and mRECIST, respectively, with a substantial interobserver agreement (k coefficient=0.79). Metastasis were independently associated with a higher risk of progression. Patients classified as responders didn't reach median survival, which was 16.2 and 15.9 months for patients classified as stable and 9.1 and 9.0 months for patients classified as progressors, in RECIST 1.1 and mRECIST criteria, respectively. We observed a wide variability in the identification of progression in MTB in clinical practice compared to the blind evaluation by radiologists mainly due to discrepancy in the evaluation of the increase in size of intrahepatic lesions. The appearance of new extrahepatic lesion or vascular invasion lesions was associated with a worse OS (p=0.032).Conclusions: RECIST 1.1 and mRECIST criteria predict OS with more responders identified by mRECIST and appearance of new extrahepatic lesion or vascular invasion was associated with a poor prognosis. A noticeable discrepancy was observed between patients classified as progressor at reviewing and the decision reached during MTB.