Meta-analysis of intermediate endpoints as surrogates for outcomes in cancer immunotherapy phase 3 trials

Cancer immunotherapy show unique efficacy kinetics that differs from conventional treatment. This may lead to prolongation of trial duration. Reliable surrogate endpoints are urgently needed. Systematic review and meta-analysis of 52,342 patients with 15 types of tumors from 77 phase 3 immunotherapy studies for advanced solid cancers found that objective response rate, disease control rate, and progression-free survival were only weakly associated with overall survival, while there was a strong correlation between 1-year survival rate and overall surival. These associations remained relatively consistent across pre-defined subgroups stratified based on tumor type, masking method, line of treatment, drug target, treatment strategy, and follow-up duration. No significant heterogeneities or publication bias were identified. The authors conclude that 1-year milestone survival was the only identified reliable surrogate endpoint for outcome in cancer immunotherapy.