Placebo therapy of benign prostatic hyperplasia: a 25-month study. Canadian PROSPECT Study Group

To analyse the efficacy, correlations and adverse-event profile of placebo therapy from the initial placebo run-in period to beyond 2 years of treatment.

The effects of placebo therapy on prostate size, maximum urinary flow rate (Qmax) and symptoms were analysed, and adverse drug experiences documented, for a period of 25 months in 303 patients randomized to the placebo arm of a controlled trial evaluating finasteride in the treatment of BPH (the Canadian PROSPECT study).

For all variables, the values during follow-up were significantly different from baseline (P < or = 0.001). Transrectal ultrasonography confirmed a progressive increase in prostate volume over 25 months (+8.4%) but Qmax improved for the first 5 months (to 1.4 mL/s over baseline) and remained 1.0 mL/s more than baseline at 25 months. The total symptom score improved by -2.9 points in the first 2 months on placebo and was ultimately 2.3 points below baseline at 25 months. The extent of the placebo response for symptoms (r=0.08, P=.180) and Qmax (r=0.04, P=0.550) was independent of age, but the response correlated with the initial severity of symptoms (r= -0.394, P < or = 0.001) and initial Qmax (r= -0.134, P=0.023). Patients with a prostate of < or = 40 mL had a clinically more important placebo response than those with larger prostates. In all, 246 patients (81.2%) reported adverse events thought to be secondary to placebo therapy. The most common complaint was urogenital (40.3%), specifically impotence (6.3%) and decreased libido (6.3%); 13.2% of patients discontinued placebo therapy because of significant adverse reactions.

Placebo therapy rapidly produces a significant improvement in Qmax and symptoms of BPH but also causes clinically important adverse effects. The beneficial effect fades but remains after 2 years.