Grading of superficial bladder cancer by quantitative mitotic frequency analysis.

A cohort of 270 superficial (stages Ta to T1) transitional cell bladder tumors was followed for more than 8 years. World Health Organization (WHO) grade, papillary status and 2 mitotic indexes were related to progression, recurrence-free survival and bladder cancer related survival during followup. Mitotic activity index and volume corrected mitotic index were significantly related to WHO grade and papillary status (p < 0.0001). WHO grade, papillary status and mitotic indexes were related significantly to progression in univariate analysis (p < 0.001) whereas in a multivariate analysis only volume corrected mitotic index included independent prognostic information (p < 0.001). Recurrence-free survival was related to volume corrected mitotic index in the entire cohort (p = 0.03) and in papillary tumors (p = 0.07). Bladder cancer related survival was related to WHO grade, papillary status, mitotic activity index and volume corrected mitotic index (all p < 0.0001). In papillary tumors mitotic activity index (p < 0.0001), volume corrected mitotic index (p < 0.0001) and WHO grade (p = 0.0036) predicted survival. In multivariate analysis mitotic activity index predicted independently recurrence-free survival in the entire cohort (p = 0.043) and in papillary tumors (p = 0.012). Bladder cancer survival in the entire cohort and in papillary tumors was related independently to volume corrected mitotic index (p < 0.001). The results show that superficial transitional cell bladder tumors can be efficiently categorized into prognostic groups by quantitative mitotic frequency analysis and the results provide a new classification system for superficial transitional cell bladder tumors.