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The Cancer of the Bladder Risk Assessment (COBRA) score: Estimating mortality after radical cystectomy

Cancer Sep 14, 2017

Welty CJ, et al. - The relative effect of tumor stage and lymph node status on cancer-specific survival (CSS) after cystectomy was gauged and a simplified risk-assessment tool was developed. A straightforward, validated risk-stratification tool was provided by the Cancer of Bladder Risk Assessment (COBRA) score. This tool entailed the relative contribution of tumor stage and lymph node involvement to patient prognosis after cystectomy for urothelial carcinoma of the bladder (UCB).


  • This study delineated 14,828 patients who underwent cystectomy with lymph node dissection for UCB from the Surveillance, Epidemiology, and End Results database (1988-2011).
  • By using stratified Kaplan-Meier and Cox proportional-hazards analyses, the relative importance of tumor stage and lymph node status with regard to CSS was assessed.
  • In addition, the patients were split randomly into development and validation cohorts.
  • Researchers conducted additional validation using overall survival on 19,362 patients from the National Cancer Data Base.
  • They created the Cancer of Bladder Risk Assessment (COBRA) tool using a Cox model incorporating age, tumor stage, and lymph node density.
  • By using observed versus expected survival plots and the Harrell concordance index, performance was validated.


  • Results reported a survival curve similar to that in patients with extravesical (T3 and T4), lymph node-negative disease (2-year CSS, 67% and 70%, respectively) in patients with muscle invasive (T2), lymph node-positive disease.
  • Each point increase in the COBRA score (range, 0-7) displayed a link with a 1.61-fold increase (95% confidence interval, 1.56-fold to 1.65-fold increase) in the risk of bladder cancer death in the development cohort.
  • Patients were accurately stratified across risk levels in the development cohort and the 2 validation cohorts (C-index, 0.712, 0.705, and 0.68, respectively) by the model.

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