Two-year follow up of silodosin on lower urinary tract functions and symptoms in patients with benign prostatic hyperplasia based on prostate size: a prospective investigation using urodynamics

Background: The aim of this research was to investigate intermediate-term effects of silodosin on lower urinary tract functions and symptoms in patients with lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH) according to prostate size, using urodynamics. Methods: A total of 70 untreated outpatients with a prostate volume <40 ml [small prostate (SP) group] and 70 with prostate volume 40 ml [large prostate (LP) group] were prospectively enrolled and treated by monotherapy with silodosin for 24 months. Changes in parameters from baseline to 3 months and 24 months after silodosin administration were assessed based on LUTS, voiding and storage function. In addition, withdrawal rates of silodosin due to insufficient effects were compared between the two groups and factors to influence the withdrawal were investigated. Results: The International Prostate Symptom Score (IPSS), bladder outlet obstruction index (BOOI), and detrusor overactivity (DO) improved significantly for the 2-year follow up in both groups as compared with the baseline. IPSS, BOOI and DO improved by 40.4%, 41.3%, and 48.1% in the SP group, 32.7%, 35.9%, and 34.4% in the LP group at 3 months, while, 44.3%, 43.5%, and 63.0% in the SP group, 22.6%, 21.1%, and 34.4% in the LP group at 24 months, respectively. Improvement rates in the IPSS and BOOI at 3 months were maintained until 24 months in the SP group, but decreased in the LP group. Storage function improvements continued in both groups for 2 years. Dropout rate due to unsatisfactory effects was significantly higher in the LP group (20% versus 8.6%). Maximum flow rate, BOOI, and intravesical prostatic protrusion had a significant influence on the withdrawal of silodosin treatment in the LP group. Conclusions: Silodosin significantly improved lower urinary tract functions for 2 years in patients with LUTS/BPH, regardless of prostate size. However, LUTS and BOO improvements tended to decrease in patients with a large prostate (>40 ml) in the intermediate term.