Effect of estimated prostate volume on silodosin-mediated improvements in the signs and symptoms of BPH: does prostate size matter?

OBJECTIVE: The uroselective α-blocker silodosin significantly improved International Prostate Symptom Score (IPSS) in two 12-week, double-blind (DB), placebo-controlled Phase III studies in men aged ≥ 50 years with symptoms of benign prostatic hyperplasia (BPH) and maintained symptom improvement during a 9-month open-label (OL) extension. This post-hoc analysis evaluated the effects of estimated prostate volume (EPV) on silodosin-mediated symptom improvement. METHODS: Patients were stratified by EPV (<30 mL or ≥ 30 mL) calculated from prostate-specific antigen (PSA) concentrations using a published algorithm. Group comparisons were done by analysis of covariance with last observations carried forward. RESULTS: Of 890 patients with PSA baseline data, 192 had EPV < 30 mL and 698 had EPV ≥ 30 mL. During DB treatment, silodosin was associated with significant symptom improvement (adjusted mean difference versus placebo) in men with EPV < 30 mL (−2.0; P = 0.038) and those with EPV ≥ 30 mL (−3.0; P < 0.0001). Among patients who received silodosin during DB treatment, changes from baseline in IPSS to the end of OL extension (mean ± standard deviation) were similar for EPV < 30 mL (n = 60, −7.0 ± 6.8) and EPV ≥ 30 mL (n = 242, −8.0 ± 7.1; P = 0.416). Also, among patients who received placebo as DB treatment, symptom improvement at the end of OL extension was similar for EPV < 30 mL (n = 62, −6.2 ± 8.1) and EPV ≥ 30 mL (n = 275, −6.7 ± 6.1; P = 0.339). CONCLUSION: Silodosin effectively relieved BPH-related symptoms for up to 12 months, irrespective of prostate size, including in patients with enlarged prostates.