EXPRESSION OF RETINOBLASTOMA GENE (RB) PROTEIN IN T12MO PROSTATIC ADENOCARCINOMA

The expression of Rb protein was analysed by immunocytochemical method s in 118 patients with T12MO prostatic adenocarcinoma who were followe d-up for more than 12 years. Rb protein was expressed in 117/118 (99%) tumours. The fraction of positive nuclei was (mean +/- SD, 92 +/- 19% ) and only one tumour was completely negative for Rb protein. Abnormal expression of the Rb protein (in fewer than 90% of cells) was indepen dent of the T category while there was a significant relationship betw een DNA ploidy (P = 0.0138), S-phase fraction (P = 0.0042) and express ion of the Rb protein. Abnormal expression of the Rb protein had no pr ognostic value while T category (P = 0.0017), Gleason score (P = 0.009 7), DNA ploidy (P = 0.0034), S-phase fraction (P = 0.0179) and mitotic index (P = 0.0001) were significant prognostic factors. In multivaria te analysis the only independent predictor was the mitotic index [Risk ratio (RR) (95%CI)= 7.4(2.4-22.5), P = 0.004]. The results show that Rb protein immunohistochemistry has hardly any prognostic significance in prostatic adenocarcinoma whereas direct measurement of cell prolif erative activity contains significant prognostic information.