Reply to Michael Froehner, Rainer Koch and Manfred P. Wirth's letter to the editor re: Roman Mayr, Matthias May, Thomas Martini, et al. Comorbidity and performance indices as predictors of cancer-independent mortality but not of cancer-specific mortality after radical cystectomy for urothelial carcinoma of the bladder. Eur Urol 2012;62:662-70