| Antiandrogen, ATC code L02 B B03Bicalutamide is a non-steroidal antiandrogen, devoid of other endocrine activity. It binds to the wild type or normal androgen receptor without activating gene expression, and thus inhibits the androgen stimulus. Regression of prostatic tumours results from this inhibition. Clinically, discontinuation of Bicalutamide can result in the 'antiandrogen withdrawal syndrome' in a subset of patients.Bicalutamide 150 mg was studied as a treatment for patients with localised (T1-T2, N0 or NX, M0) or locally advanced (T3-T4, any N, M0; T1-T2, N+, M0) non- metastatic prostate cancer in a combined analysis of three placebo controlled, double-blind studies in 8113 patients, where Bicalutamide was given as immediate hormonal therapy or as adjuvant to radical prostatectomy or radiotherapy (primarily external beam radiation). At 7.4 years median follow up, 27.4% and 30.7% of all Bicalutamide and placebo-treated patients, respectively, had experienced objective disease progression. A reduction in risk of objective disease progression was seen across most patients groups but was most evident in those at highest risk of disease progression. Therefore, clinicians may decide that the optimum medical strategy for a patient at low risk of disease progression, particularly in the adjuvant setting following radical prostatectomy, may be to defer hormonal therapy until signs that the disease is progressing.No overall survival difference was seen at 7.4 years median follow up with 22.9% mortality (HR=0.99; 95% CI 0.91 to 1.09). However, some trends were apparent in exploratory subgroup analyses.Progression-free survival and overall survival data for patients with locally advanced disease are summarised in the following tables: Table 1 Progression-free survival in locally advanced disease by therapy sub-group Analysis population | Events (%) in Bicalutamide patients | Events (%) in placebo patients | Hazard ratio (95% CI) | Watchful waiting | 193/335 (57.6) | 222/322 (68.9) | 0.60 (0.49 to 0.73) | Radiotherapy | 66/161 (41.0) | 86/144 (59.7) | 0.56 (0.40 to 0.78) | Radical prostatectomy | 179/870 (20.6) | 213/849 (25.1) | 0.75 (0.61 to 0.91) |
Table 2 Overall survival in locally advanced disease by therapy sub-group Analysis population | Deaths (%) in Bicalutamide patients | Deaths (%) in placebo patients | Hazard ratio (95% CI) | Watchful waiting | 164/335 (49.0) | 183/322 (56.8) | 0.81 (0.66 to 1.01) | Radiotherapy | 49/161 (30.4) | 61/144 (42.4) | 0.65 (0.44 to 0.95) | Radical prostatectomy | 137/870 (15.7) | 122/849 (14.4) | 1.09 (0.85 to 1.39) | For patients with localised disease receiving Bicalutamide alone, there was no significant difference in progression free survival. In these patients there was also a trend toward decreased survival compared with placebo patients (HR=1.16; 95% CI 0.99 to 1.37). In view of this, the benefit-risk profile for the use of Bicalutamide is not considered favourable in this group of patients.In a separate programme, the efficacy of Bicalutamide 150 mg for the treatment of patients with locally advanced non-metastatic prostate cancer for whom immediate castration was indicated, was demonstrated in a combined analysis of 2 studies with 480 previously untreated patients with non-metastatic (M0) prostate cancer. At 56% mortality and a median follow-up of 6.3 years, there was no significant difference between Bicalutamide and castration in survival (hazard ratio = 1.05 [CI 0.81 to 1.36]); however, equivalence of the two treatments could not be concluded statistically.In a combined analysis of 2 studies with 805 previously untreated patients with metastatic (M1) disease at 43% mortality, Bicalutamide 150 mg was demonstrated to be less effective than castration in survival time (hazard ratio = 1.30 [CI 1.04 to 1.65]), with a numerical difference in estimated time to death of 42 days (6 weeks) over a median survival time of 2 years.Bicalutamide is a racemate with its antiandrogen activity being almost exclusively in the R-enantiomer.
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