Purpose: Histopathological grade remains the most important predictive factor for the prognosis of nonmuscle invasive bladder cancer. We defined the clinical reliability of the 2004 WHO and International Society of Urological Pathology histological classification system compared with that of the 1973 WHO system for Ta primary bladder tumors. Materials and Methods: We evaluated 270 consecutive patients with a first episode of low grade pTa bladder cancer at transurethral resection of the bladder between 2004 and 2008. Grade was assigned by a single uropathologist simultaneously as low grade, and as G1 or G2 according to the 2004 and 1973 WHO classification systems, respectively. All patients received a single early prophylaxis instillation of 50 mg epirubicin as the only adjuvant treatment. Followup included urine cytology and cystoscopy 3 months after resection and every 6 months thereafter for 5 years. Univariate and multivariate analysis of recurrence-free and progression-free survival was done with the Kaplan-Meier method and the log rank test. Results: Mean patient age was 67.3 years (median 67, range 27 to 91). Of the patients 50 were female (18.1%) and 220 (81.9%) were male. According to the 1973 system, grade was G1 in 87 patients (32.2%) and G2 in 183 (67.8%). Median followup was 25 months (mean 27.4, range 3 to 72). The 5-year recurrence-free survival rate was 49.4% for the low grade population, and 62% and 40% for the G1 and G2 groups, respectively (p = 0.004). The 5-year progression-free survival rate was 93% for the low grade population, and 97.6% and 93.3% for the G1 and G2 groups, respectively (p = 0.06). Conclusions: The 1973 WHO classification system predicted the risk of recurrence in primary pTa cases more accurately than the 2004 WHO system. Each classification had the same accuracy when predicting the risk of progression. Our study confirms the clinical reliability of the new histological classification in clinical practice from a prognostic point of view.
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