Is botulinum neurotoxin type A (BoNT-A) a novel therapy for lower urinary tract symptoms due to benign prostatic enlargement? A review of the literature

Abstract

Context: The intraprostatic injection of botulinum neurotoxin type A (BoNT-A) is a minimally invasive but still-experimental treatment of lower urinary tract symptoms (LUTS) due to benign prostatic enlargement (BPE) based on an off-label use of the drug.

Objective: Report the mechanisms of action of BoNT-A on the prostate as well as the efficacy and safety of intraprostatic BoNT-A injection according to various injection protocols.

Evidence acquisition: We searched the Medical Literature Analysis and Retrieval System Online (MEDLINE) database and the abstract volumes of the 2005, 2006, and 2007 European Association of Urology (EAU), American Urological Association (AUA) and International Continence Society (ICS) meetings for studies on intraprostatic BoNT-A injection.

Evidence synthesis: Five experimental studies and 10 clinical studies were found. The level of evidence is 1b for one study and 3 for the other studies, with grades of recommendation of A and C, respectively. The experimental studies report induced relaxation of the prostate, atrophy, and reduction of its size through inhibition of the trophic effect of the autonomic system on the prostate gland. In the clinical studies, all patients had LUTS due to BPE and prostate volume varied from <20 ml to >80 ml. The dose varied from 100U to 300U of Botox((R)). The injection was performed transperineally, transrectally, or transurethrally under general, local, or without anesthesia. The follow-up period ranged from 3 mo to 19.8 mo. All studies reported an improvement of maximum urinary flow rate, quality-of-life index and reduction of International Prostate Symptoms Score, prostate-specific antigen (PSA) level, post-void residual volume, and prostate volume. Local or systemic side effects were rare. Only patients with retention needed a urethral drainage catheter.

Conclusions: BoNT-A intraprostatic injection provides improvement in patients with LUTS due to BPE refractory to medical treatment. However, there is a need for large placebo controlled-studies and long-term results. So far the therapy is still experimental.