P53 expression, ploidy and progression in pT1 transitional cell carcinoma of the bladder

To investigate a potential role for overexpression of the p53 protein in the identification of pT1 bladder tumours destined to progress.

The protein expression of the tumour suppressor gene p53, nuclear ploidy and tumour grade were studied in 25 patients with pT1 bladder tumours. Follow-up data was available for 21 tumours over a 10 year period. p53 expression was determined by immuno-histochemistry on paraffin embedded sections and flow cytometry was performed on cell suspensions derived from the same blocks.

Ten of 21 (48%) tumours progressed to muscle invasive disease. Nuclear staining for the protein was seen in 16 (64%) tumours and of these nine (56%) progressed. All tumours with abnormal DNA content and all high grade tumours demonstrated overexpression of p53. Significantly more patients with high levels of p53 expression (> 10% nuclear staining) progressed compared with tumours with less than 10% of nuclei staining (P = 0.007). However, grade was the most specific predictor of progression (100%), with all grade 3 tumours progressing and grade was also the most significant prognostic indicator in terms of survival (P = 0.025).

Tumour grade is likely to remain as the most useful aid to management decisions in pT1 bladder tumours.