Relationship Between Progression-Free Survival, Objective Response Rate, and Overall Survival in Clinical Trials of PD-1/PD-L1 Immune Checkpoint Blockade: A Meta-Analysis

Abstract

PD-1/PD-L1 immune checkpoint blockade (ICB) has improved overall survival (OS) in solid tumor trials; however, parallel improvements in Response Evaluation Criteria in Solid Tumors (RECIST)-based surrogate end points, progression-free survival (PFS), and objective response rate (ORR), are not always observed. Here, we assess the surrogacy of PFS/ORR for OS with ICB therapy across advanced/metastatic tumors. In a trial-level analysis (N = 40 randomized trials), PFS, ORR, and OS treatment effects were correlated (Spearman's rho). In a patient-level analysis, data were extracted from available trials of durvalumab; the correlation of PFS and OS was evaluated (Bayesian normal-induced-copula-estimation model) and the ordinal association between objective response and OS hazard ratio (HR) were assessed with concordance index measures. High correlation was observed between PFS HR and OS HR in intention-to-treat (ITT; rho = 0.76) and PD-L1-enriched populations (0.74); modest (or limited) benefit in PFS was associated with meaningful improvement in OS. Moderate correlations were observed between ΔORR and OS HR: ITT, -0.63; PD-L1-enriched, -0.53. At the patient level, a positive association was observed between PFS and OS in non-small cell lung cancer (Kendall's Tau = 0.793; 95% confidence interval, 0.789-0.797), head and neck squamous cell carcinoma (0.794; 0.789-0.798), and bladder cancer (0.872; 0.869-0.875). Objective responders had significantly better OS (concordance index > 0.9) than nonresponders across these tumor types. Modest (or limited) improvement in RECIST-based end points did not rule out meaningful OS benefit, indicating they are imperfect surrogates and do not fully capture ICB clinical benefit. Therefore, caution is advised when basing early discontinuation of novel ICB agents on these end points.