Are radiological endpoints surrogate outcomes of overall survival in hepatocellular carcinoma treated with transarterial chemoembolization?

Background& Aims Time to progression (TTP) and progression-free survival (PFS) are commonly used as surrogate endpoints in oncology trials. We aimed to assess the surrogacy relationship of TTP and PFS with overall survival (OS) in studies of transarterial chemoembolization (TACE) for unresectable hepatocellular carcinoma (u-HCC) by innovative methods. Methods A search of databases for studies of TACE for u-HCC reporting both OS and TTP or PFS was performed. Individual patient data were extracted from TTP/PFS and OS Kaplan-Meier curves of TACE arms. Pooled median TTP and OS were obtained from random-effect model. The surrogate relationships of hazard ratios (HRs) and median TTP for OS were evaluated by the coefficient of determination R-2. Results We identified 13 studies comparing TACE vs systemic therapy or vs TACE plus systemic therapy and including 1932 TACE-treated patients. Pooled median OS was 11.2 months (95% confidence interval [95%CI] 7.9-17.8), and pooled median TTP was 5.4 months (95%CI 3.8-8.0). Heterogeneity among studies was highly significant for both outcomes. The correlation between HR TTP and HR OS was moderate (R-2 = 0.65. 95%CI 0.08-0.81). R-2 value was 0.04 (95%CI 0.00-0.35) between median TTP and median OS. Conclusion In studies of TACE for u-HCC, the surrogate relationship of radiology-based endpoints with OS is moderate. Multiple endpoints including hepatic decompensation, macrovascular invasion and extrahepatic spread are needed for future trials comparing systemic therapies or combination of TACE with systemic therapies vs TACE alone.