Objective   To evaluate the immunoreactivity of the Ki-67 protein in stage T1 non-muscle invasive bladder cancer (NMIBC) and determine the predictive role of Ki-67 expression.

  Methods   A retrospective study was performed on 102 patients with stage T1 NMIBC who underwent transurethral resection at the Tianjin Medical University Cancer Institute and Hospital from June 2011 to October 2013. The expression of Ki-67 was evaluated using immunohistochemical assay and scored for intensity and area of staining. Then, the association between Ki-67 expression and categorical variable was analyzed. The predictive role of Ki-67 expression in tumor recurrence and progression was assessed by univariate and multivariate analyses.

  Results   Of the 102 patients, 20 (19.6%) had tumor recurrence and 12 (11.8%) progressed to muscle invasive disease, with a median follow-up of 43 months (range, 24-57 months). A high expression of Ki-67 (determined using receiver operating characteristic curve analysis) was observed in 32 (31.4%) cases. This high expression of Ki-67 correlated with tumor grade (P < 0.05) but not with gender, age, tumor number, and tumor size (P > 0.05). Univariate analysis revealed a correlation of tumor progression with Ki-67 expression, tumor grade, tumor number, and prior recurrence rate (P < 0.05) but not between Ki-67 expression and tumor recurrence (P > 0.05). Cox multivariate regression analysis showed that high Ki-67 expression (P=0.043) and prior recurrence rate (P=0.018) are independent risk factors for predicting tumor progression.

  Conclusion   High Ki-67 expression is an independent prognostic factor for predicting tumor progression. Detection of its expression could predict the risk for progression in stage T1 NMIBC and provide the basis for appropriate treatment.