Background: OS is a critical endpoint for adjuvant RCC trials testing the benefit of early systemic therapy to increase cure rates, but requires long duration and significant patient resources. We explored the potential use of DFS as a surrogate for OS when assessing the efficacy of adjuvant therapy in localized RCC. Methods: We performed a systematic literature review following the PRISMA statement. Inclusion criteria required randomized controlled trials (RCT) for adjuvant systemic therapy in localized RCC, which reported on both DFS and OS. DFS was defined from randomization or nephrectomy (R/N) to the first evidence of clinical recurrence (loco-regional or distant) or death from any cause. OS was defined from R/N to death from any cause. We extracted data on hazard ratio (HR) and 5-year event free rate from Kaplan Meier estimates. We performed a meta-analysis and correlated these estimates for OS and DFS, weighted by number of DFS events. R-square >0.7 would indicate a strong correlation and potential surrogacy. Results: Of the more than 315 studies screened, 10 studies investigating various forms of cytokine and vaccine immunotherapy and angiogenesis inhibitors (e.g., sunitinib, sorafenib, thalidomide) between 1987 and 2016 were eligible for the analyses. The total enrolled patients were 5,497, with median follow-up ranging 3 to 10 years. Conclusions: Across trials of adjuvant systemic therapy for localized RCC, we observed a moderate correlation between 5 yr DFS and OS rate and between treatment effects (HRs) on these endpoints. Future meta-analyses of more mature trials in the era of modern adjuvant targeted therapy are needed to evaluate the surrogacy of intermediate endpoints. Further granularity may be achieved using individual patient data to assess different and earlier time points for surrogacy than are commonly reported.

*10 (trials) * 2 (arms) = 20 units

**Natural log transformed