Evaluation of P53 protein overexpression, Ki67 proliferative activity and mitotic index as markers of tumour recurrence in superficial transitional cell carcinoma of the bladder.

OBJECTIVES

To confirm the interrelationship between p53, ki67, mitotic index with others known prognostic factors such us stage, grade, multifocality, tumour size, history of recurrence in transitional cell carcinoma (TCC) of the bladder and to determine the prognostic impact of p53, Ki67 and mitotic index in predicting recurrence in superficial bladder cancer.

METHODS

Two hundred and fourteen patients with apparently superficial TCC of the bladder underwent TURBT and the 192 histologically Ta-T1 were divided into 104 primary lesions (group 1, mean follow-up 26 months) and 88 recurrent tumours (group 2, mean follow-up 28 months). Data concerning focality, tumour size, number of recurrences and recurrence-free survival were considered in each patients. All samples were immunohistochemically stained with p53 and Ki67 monoclonal antibodies. Mitotic index (MI) was calculated on haematoxylin and eosin stained sections.

RESULTS

Recurrence-free survival was significantly lower in superficial recurrent tumours (group 2) compared with primary tumours (group 1). P53 staining was correlated with grade and stage for both 5 and 20% positivity thresholds. Ki67 and MI were significantly different over strata defined by stage, grade and focality in both patients groups but only Ki67 showed a correlation with p53 status. Recurrence-free survival could not be predicted either by p53 status or MI. A 20% cut-off level of Ki67 staining resulted a good predictor of recurrence in group 1 Ta-T1/G1-G2 tumours (p = 0.03). Only Ki67 and multifocality were found to be independent prognostic factors of recurrence in multivariate analysis. Stratifying Ta-T1/G1-G2 patients according to these variables, Ki67 provided a useful tool to predict early recurrence in monofocal lesions from both groups.

CONCLUSIONS

P53 and MI despite a fairly good correlation with traditional prognostic factors in bladder TCC seem to play no role in the prediction of tumoural recurrence. A Ki67 index over 20% predicts those single well-differentiated (Ta-T1/G1-G2) tumours which are likely to recur within one year of treatment.