Botulinum toxin shows a notable capacity to reduce the prostate volume

Thursday, 9 April 2009 - Botulinum neurotoxin subtype A (BoNT-A) is the most powerful biological toxin known to man. Prof. Francisco Cruz, et al. reported on the notable capacity of BoNT-A to reduce the prostate volume. Such capacity can be applied in the treatment of urinary retention or LUTS refractory to standard medical treatment occurring in patients with severe contra-indications to undergo surgery.

BoNT-A is already approved for the treatment of strabismus and blepharospasm., skeletal muscle dystonias and hyperhidrosis. Off-label applications in the lower urinary tract include the management of detrusor overactivity, interstitial cystitis (bladder pain syndrome) and detrusor-sphincter dyssynergy.

Recently, BoNT/A injection in the rat prostate was shown to cause a rapid decrease in prostate volume and weight. These findings were subsequently confirmed in the human prostate.

Injection of BoNT/A caused a rapid decrease in the volume of enlarged prostates, ranging between 30 to 50% of the initial volume. The effects of BoNT/A were attributed by a recent experimental study to the disruption of the sympathetic innervation of the gland, leading both to a generalised apoptosis in the prostate and to a marked decrease in its smooth muscle tonus.

BoNT/A can be easily injected in the prostate, as an office procedure, by transrectal or transperineal route, using fine needles advanced into the gland under ultrasound guidance. Thus, no wonder BoNT/A is emerging as a new treatment for frail patients with LUTS or urinary retention caused by benign prostatic enlargement refractory to standard medical treatment.

The objective is to avoid the use in these patients of more invasive therapies including transurethral resection of the prostate or open prostatectomy. These surgical procedures are not without serious risks in an elderly population. Laser vaporisation and ethanol injections have been suggested as alternatives for poor surgical candidates but still requires anaesthetic support.

The authors recently had the opportunity to treat 46 patients with 200 U of BoNT/A (Botox) diluted in 8 ml (4 ml in each lobe). All had severe contra-indications to standard surgery. In a group of 21 patients in refractory urinary retention prostate volume decreased from 70 ml to 47ml at 3 months (p<0.05).

At three months 17 patients (81%) could void with a Qmax of 10 ml/sec and a post void residual volume of 92 ml.. Eleven of these patients were followed regularly up to 18 months. Prostate volume reached the minimum value at 6 month to experience a progressive increase thereafter and regain baseline volume by the 18th month after injection.

Nevertheless all the 11 patients maintained spontaneous voiding by the 18th month with an average flow of 10 ml/s, an IPSS score of 11.2 and without remarkable post void residual volumes. In 25 patients with LUTS refractory to medical treatment prostate volume decreased from 75 ml to 44 ml at 3 months (p<0.05).

This was accompanied by an increased Qmax from 9.6 to 13.8 ml/sec (p<0.05), a decrease in post void residual volume (108 to 60 ml, p<0.05) and an improvement in IPSS (20.6 to 10.6, p<0.05). Side effects were remarkable rare. Two patients developed clinical prostatitis requiring prolonged antibiotherapy in addition to the prophylactic antibiotic given at the moment of the BoNT/A injection.

No symptoms of botulism were reported by any of the patients. In patients with sexual activity before injection, no ejaculatory or erectile dysfunctions were reported

Source: Prof. Francisco Cruz, Hospital de S. João, Porto (PT)

Edited by: FGR

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