Six-Month Progression-Free Survival as the Primary Endpoint to Evaluate the Activity of New Agents as Second-line Therapy for Advanced Urothelial Carcinoma

This study examined the association of progression-free survival at 6 months with overall survival in the context of second-line therapy of advanced urothelial carcinoma in pooled patient-level data from 10 phase II trials and then externally validated in a large phase III trial. Progression-free survival at 6 months was significantly correlated with overall survival and is an innovative primary endpoint to evaluate new agents in this setting. Objective: Second-line systemic therapy for advanced urothelial carcinoma (UC) has substantial unmet needs, and current agents show dismal activity. Second-line trials of metastatic UC have used response rate (RR) and median progression-free survival (PFS) as primary endpoints, which may not reflect durable benefits. A more robust endpoint to identify signals of durable benefits when investigating new agents in second-line trials may expedite drug development. PFS at 6 months (PFS6) is a candidate endpoint, which may correlate with overall survival (OS) at 12 months (OS12) and may be applicable across cytostatic and cytotoxic agents. Methods: Ten second-line phase II trials with individual patient outcomes data evaluating chemotherapy or biologics were combined for discovery, followed by external validation in a phase III trial. The relationship between PFS6/RR and OS12 was assessed at the trial level using Pearson correlation and weighted linear regression, and at the individual level using Pearson chi-square test with Yates continuity correction. Results: In the discovery dataset, a significant correlation was observed between PFS6 and OS12 at the trial (R-2 = 0.55, Pearson correlation = 0.66) and individual levels (82%, K = 0.45). Response correlated with OS12 at the individual level less robustly (78%,. = 0.36), and the trial level association was not statistically significant (R-2 = 0.16, Pearson correlation = 0.37). The correlation of PFS6 (81%,K = 0.44) appeared stronger than the correlation of response (76%, K = 0.17) with OS12 in the external validation dataset. Conclusions: PFS6 is strongly associated with OS12 and appears more optimal than RR to identify active second-line agents for advanced UC. (C) 2014 Elsevier Inc. All rights reserved.