Prognostic significance of a grading system considering tumor heterogeneity in muscle-invasive urothelial carcinoma of the urinary bladder

Abstract

The fact that urothelial carcinomas (UC)often contain areas with different histologicgrades has been recently shown to bear someprognostic relevance. Here we examined theprognostic significance of a grading systemconsidering tumor heterogeneity inmuscle-invasive bladder carcinomas.151 UC treated by radical cystectomy wereincluded. According to the World HealthOrganization/International Society ofUrological Pathology (WHO/ISUP) classification,histologic grade was low-grade (LG) in 8 andhigh-grade (HG) in 143 cases. 65 HG tumorswhich focally harbored LG areas were assignedto mixed-type (MT) carcinomas. Mean follow-upwas 50 months.While the WHO/ISUP classification showedno significant correlation withdisease-specific survival (p = 0.3995 bylog-rank test), stratification into LG/MT andHG tumors had a significant prognosticrelevance (p = 0.0404). Nodal status wasidentified as the only independent prognosticfactor (p = 0.0001 by multivariate analysis).In this respect, stratification into LG/MT andHG tumors missed the level of statisticalsignificance by a norrow margin (p = 0.07 bymultivariate analysis), but it turned outbetter than tumor category (p = 0.08).In conclusion, a grading systemconsidering tumor heterogeneity may improve thepredictive power of the WHO/ISUP classificationin muscle-invasive UC of the urinary bladder.Although the two-tired grading system proposedin this study was not identified as anindependent prognostic factor, it may help toobtain additional prognostic information onpatients with advanced bladder cancer treatedby radical cystectomy.