Water Vapor Thermal Ablation of the Prostate

Excerpt

Water vapor thermal ablation of the prostate (WVAP) is a minimally invasive surgical therapy for symptomatic benign prostatic hyperplasia (BPH). WVAP was introduced and approved by the United States Food and Drug Administration in 2015. The incidence of BPH increases with age; 50% to 75% of men 50 years and older and 80% of men 70 years and older report clinically significant lower urinary tract symptoms due to BPH. Lower urinary tract symptoms from BPH-induced extrinsic compression of the prostatic urethra include but are not limited to urinary urgency, frequency, hesitancy, intermittency, incomplete bladder emptying, nocturia, and a diminished urinary stream. BPH is also associated with considerable morbidity characterized by urinary retention, recurrent urinary tract infections, urolithiasis, persistent hematuria, and renal insufficiency.

Standard therapies for symptomatic BPH include continuous oral medications and various surgical procedures. The goal of WVAP is to relieve extrinsic compression of the prostatic urethra by inducing coagulative necrosis of hyperplastic prostatic tissue via the directed application of radiofrequency-generated thermal energy in the form of water vapor or steam. Water vapor has a lower mass and density than prostatic tissue and moves easily through cellular interstitial spaces. However, water vapor cannot pass through natural barriers such as the tissue planes separating prostatic zones. This inherent characteristic of water vapor promotes the specific targeting of the prostatic transition zone where most BPH occurs, minimizing the risk of necrosis to the bladder neck, striated urinary sphincter, prostatic capsule, seminal vesicles, prostatic vascular supply, and rectum.

WVAP may be performed in the office or operating room. While the procedure requires an average of 10 minutes to perform, complete resorption of necrotic prostatic tissue may take up to 12 months. The resolution of lower urinary tract symptoms occurs progressively, and optimal results may not be achieved until tissue resorption is complete.

The effectiveness of WVAP in alleviating clinically significant lower urinary tract symptoms has been reviewed in more than 20 published series and reports, including 5 prospective randomized studies and 2 randomized-controlled trials involving more than 2,000 patients followed for up to 5 years. Significant improvements were noted consistently in troubling symptoms, overall quality of life, post-void residual volumes, and peak urinary flow rates. Additionally, WVAP is the only minimally invasive surgical therapy with proven efficacy for reducing lower urinary tract symptoms in patients with prostatic volumes of greater than 80 mL or obstructing median prostatic lobes.