title: Disease-Free Survival at 2 and 3 Years is a Significant Early Surrogate Marker Predicting the 5-Year Overall Survival in Patients Treated with Radical Cystectomy for Urothelial Carcinoma of the Bladder: External Evaluation and Validation in a Cohort of Korean Patients.
abstract: OBJECTIVE
  We aimed to externally validate the association of 2- and 3-year disease-free survival (DFS) with 5-year overall survival (OS) in patients treated with radical cystectomy (RC) for urothelial carcinoma (UC) of the bladder.
  
  
  METHODS
  We reviewed the clinical data of 422 patients who underwent RC for UC of the bladder in our institution between 1991 and 2012. Survival curves were plotted with the Kaplan-Meier method. The Kappa statistic and Kendall tau-b test were used to assess the agreements between 2- and 3-year DFS and 5-year OS.
  
  
  RESULTS
  In the entire study population, 2- and 3-year DFS and 5-year OS rates were 76.4, 71.5, and 67.4%, respectively. All Kappa and Kendall's tau-b test values for agreements between 2- and 3-year DFS and 5-year OS were more than 0.40, indicating moderate agreement for all patients and in each patient subgroup selected according to specific variables (all p-values <0.05). Kaplan-Meier analysis for DFS and Cox-proportional hazard models for landmark analysis at each time point indicated that most recurrences occurred within 3 years after surgery. The 5-year OS rates of patients who were recurrence-free at each time point gradually increased to more than 95% in an extended recurrence-free interval of 12-36 months.
  
  
  CONCLUSIONS
  Our external validation results support the existing finding that 2- and 3-year DFS can be a valid early surrogate end point to predict 5-year OS after RC in patients with UC of the bladder.
authors.affiliation: Department of Urology, Seoul National University College of Medicine , Seoul , South Korea.
authors.forename: Hyung Suk
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Urology, Seoul National University College of Medicine , Seoul , South Korea.
authors.forename: Chang Wook
authors.initials: CW
authors.lastname: Jeong
authors.affiliation: Department of Urology, Seoul National University College of Medicine , Seoul , South Korea.
authors.forename: Cheol
authors.initials: C
authors.lastname: Kwak
authors.affiliation: Department of Urology, Seoul National University College of Medicine , Seoul , South Korea.
authors.forename: Hyeon Hoe
authors.initials: HH
authors.lastname: Kim
authors.affiliation: Department of Urology, Seoul National University College of Medicine , Seoul , South Korea.
authors.forename: Ja Hyeon
authors.initials: JH
authors.lastname: Ku
keywords: disease-specific survival; overall survival; radical cystectomy; surrogate; urothelial carcinoma