p53, p21 and mdm2 expression vs the response to radiotherapy in transitional cell carcinoma of the bladder

To identify, in a retrospective study, possible molecular markers predictive of radioresponsiveness in patients with transitional cell carcinoma (TCC) of the bladder.

Patients with T2-T4a TCC treated with preoperative radiotherapy and cystectomy were included in the study if their cystectomy specimen was pT3b (in 42) or pT0 (in 17). Because treatment schedules changed over time, radiotherapy was given either as 2 Gy x 23 over 4-5 weeks with cystectomy 4-5 weeks later (in 23), or as 4 Gy x 5 during 1 week with cystectomy in the following week (in 36 patients). Protein expression of p53, mdm2 and p21 (CDKN1 A/WAF1/CIP1/SDI1) was assessed immunohistochemically in biopsies taken before radiotherapy.

There was no difference in protein expression when comparing all patients with pT0 and pT3b. However, for patients receiving 46 Gy, increased p53 expression (but not p21 or mdm2) predicted the absence of residual tumour (P = 0.005): six of seven patients with > 50% p53 expression had pT0 in the cystectomy specimen, whereas 10 of 12 patients with < or = 5% expression had pT3b. Over-expression of p53 correlated with longer overall (P = 0.045) and cancer-specific survival (P = 0.020).

The expression of mdm2 or p21 did not predict radioresponsiveness in patients with TCC of the bladder. The role of p53 remains unclear; the view that p53 over-expression confers radioresistance in bladder cancer is not supported.