Prognostic role of Ki-67 expression in determination of risk of non-muscle invasive bladder cancer recurrence

Introduction. To increase accuracy of disease prognosis in patients with bladder cancer we propose determination of expression level of several tumor markers. Objective is evaluation of prognostic significance of Ki-67 expression level in risk of non-muscle invasive bladder cancer recurrence.

Materials and methods. To perform immunohistochemistry analysis of Ki-67 we used surgery material of 83 patients who underwent primary transurethral bladder resection due to non-muscle invasive cancer. We performed an analysis of correlation between Ki-67 expression level in malignant tissue removed by transurethral resection and characteristics of tumor development. We evaluated the role of Ki-67 in stratification of recurrence risk by comparing the level of Ki-67 antigen expression in patients with recurrent non-muscle invasive bladder cancer and in relapse-free patients. We present evaluation of sensitivity, specificity, and prognostic value of quantitative determination of Ki-67 expression level in relation to non-muscle invasive bladder cancer recurrence.

Results. During the follow-up period, 41 cases of non-muscle invasive bladder tumor recurrence were observed. Quantitative value of the Ki-67 marker correlated with tumor differentiation grade G, malignancy grade, invasion into submucosal and muscle layers, presence of primary process, and tumor recurrence. In comparison with relapse-free patients, a significantly higher level of Ki-67 expression was observed in patients with cancer recurrence (р = 0.0035). We have determined a threshold quantitative value of Ki-67 (48 %) indicating disease recurrence. Presence of a threshold value of the Ki-67 marker showed moderate sensitivity level (less than 71 %) with relatively low specificity level (57 %). However prognostic level wasn’t high (between 63 and 65 %).

Conclusion. In patients with recurrent non-muscle invasive bladder cancer an elevated level of Ki-67 expression was observed in comparison with relapse-free patients (test sensitivity was 70.7 %). Obviously, determination of molecular biomarkers, Ki-67 in particular, can potentially help distinguish highly malignant tumors with high progression and recurrence risk, which can significantly improve treatment results for these patients. However, this problem requires further research.