Supplementary Material for: Objective response and progression free survival contribute to prolong overall survival in atezolizumab plus bevacizumab treatment for unresectable hepatocellular carcinoma.

Introduction: Atezolizumab plus bevacizumab (Atez/Bev) is a standard treatment for unresectable hepatocellular carcinoma (HCC) due to its good anti-tumor and survival prolongation effects. Post-progression survival (PPS) has been reported to be a great contributor in the treatment with tyrosine kinase inhibitors for unrecetable HCC. This study aimed to clarify the significance of progression-free survival (PFS) or PPS of Atez/Bev treatment for HCC. Methods: We analyzed the correlations of PFS and PPS with overall survival (OS) in studies of HCC patients treated with Atez/Bev and evaluated the contribution to OS in Atez/Bev treatment with patients at our institutions as clinical practice. Results: Analysis of 18 studies involving 2,937 patients treated with Atez/Bev found that PPS had a stronger correlation with OS (R2=0.872, p<0.001) than did PFS (R2=0.605, p=0.001). Analysis of 80 patients with unresectable HCC treated with Atez/Bev found that presence of anti-tumor responses during Atez/Bev was the most significant contributor to OS, and post-progression treatment after Atez/Bev also significantly contribute to OS. Conclusion: The presence of anti-tumor response with tumor shrinkage during Atez/Bev treatment contributes to good OS through its durable response. Atez/Bev treatment could be considered as first-line treatment for unresectable HCC. However, there is a need for optimal biomarkers for good-anti-tumor response.