Evaluation of Retinoblastoma Gene Product (RB) as A Prognostic Indicator in Bladder Carcinoma

Despite precise pathologic staging and grading, we are unable to predict clinical outcome in patients with bladder cancer. The retinoblastoma susceptibility gene (RB) a prototype of tumour suppressor genes, thought to function as a cell cycle regulator, has recently been associated with development and/or progression of bladder cancer, as well as sarcoma and small cell lung cancer. Purpose: The aim of this study was to investigate the hypothesis that altered patterns of RB expression correlate with prognosis and with tumour cell growth fraction in bladder cancer. Methods: Tumours from 40 patients with primary transitional cell carcinoma were studied. Expression of RB gene product was assessed immuno histochemically. The proportion of cells expressing the ki 67 antigen was also detected. Results: Three patterns of RB protein staining were observed, absent n = 12, heterogenous n = 23 and strongly homogenous n = 5. Cases with loss of RB protein and those with apparent over expression were considered to have an altered RB protein expression. Altered expression of RB was significantly associated with muscle invasive growth and high tumour grade (ρ< 0.0001, ρ< 001) respectively. The 5 years survival rate was significantly decreased in patients with altered RB protein expression compared with patients with normal expression of RB (ρ< 0.05). There were significant differences in the ki 67 index between poorly (G3) and better (G I/G2) differentiated tumours and between invasive and non muscle invasive tumours. Conclusion: This study suggests that altered patterns of RB protein expression may be an important prognostic variable in patients presenting with invasive bladder cancer