Rezūm II: Convective Water Vapor Thermal Therapy Versus Sham for BPH
Rezūm II was a multicenter, participant-blinded, sham-controlled randomized trial in 197 men aged 50 or older with moderate-to-severe lower urinary tract symptoms, IPSS of 13 or higher, peak flow of 15 mL/s or less and prostate volume of 30–80 cc that compared convective water vapor thermal therapy (Rezūm) with rigid cystoscopy and simulated treatment sounds. At 3 months, mean IPSS fell by 11.2 points with water vapor therapy and by 4.3 points with the sham procedure (p < 0.0001).[1]
- Design and population
- Multicenter, sham-controlled, participant-blinded randomized trial. Men aged 50 or older with IPSS 13 or higher, peak flow rate 15 mL/s or less and prostate volume 30–80 cc, with or without a median lobe.
- Arms
- Convective water vapor thermal therapy (Rezūm) versus sham rigid cystoscopy with simulated treatment sounds
- Report and follow-up
- 2015 · 3-month randomized comparison; treatment arm followed to 12 months
| Endpoint | Results | Effect | Finding |
|---|---|---|---|
| Change in IPSS from baseline at 3 months (mean ± SD; mean difference is treatment minus sham) | −11.2 ± 7.6 vs −4.3 ± 6.9 | difference -6.9; CI -9.06–-4.74; P <0.0001 | Met |
| Composite at 3 months: new severe retention lasting more than 21 days, rectourethral fistula, or rectal or gastrointestinal perforation (treatment arm only) | 1/136 | — | Met |
Harms: Clavien–Dindo grade III–V adverse events: 7/136 (5.1%) vs 0/61; Clavien–Dindo grade I–II adverse events: Risk ratio 1.89 (95% CI 1.15–3.11) for treatment versus sham, low-certainty evidence; examples were dysuria, hematuria, frequency, urgency, hematospermia and urinary infection. The primary report describes adverse events as mild to moderate and quickly resolved.; Catheterization before discharge: 122/135 (90.4%) vs 12/61 (19.7%)
Design
Fifteen US centers enrolled men from September 2013 to August 2014; 384 were screened and 197 were randomized 2:1 by permuted blocks stratified by center and baseline IPSS.[2] Eligibility required a peak flow of 5–15 mL/s with a voided volume of at least 125 mL and a postvoid residual of 250 mL or less.[1] The registry exclusions include any prior invasive prostate intervention or other prostate surgery, a penile implant or urethral or prostatic stent, spontaneous urinary retention treated with an indwelling transurethral or suprapubic catheter in the preceding 6 months (a resolved provoked episode was allowed), urethral stricture or bladder neck contracture, neurogenic bladder and known prostate or bladder cancer; a median lobe was not an exclusion.[1][3] Treatment-arm men averaged 63.0 years, an IPSS of 22.0, an IPSS quality-of-life score of 4.4, a prostate volume of 45.9 cc, a peak flow of 9.9 mL/s and a postvoid residual of 82.4 mL; 72.5% of the cohort had an IPSS of 19–35.[2]
The control procedure was a 19–21 Fr rigid cystoscopy with simulated active-treatment sounds, and participants were unblinded after the 3-month visit. The Cochrane review judged performance bias high risk because the urologists performing the procedures could not be blinded.[2][4]
The primary efficacy endpoint was the change in IPSS from baseline at 3 months. The trial was powered at 80% (one-sided alpha 0.025) to test whether the IPSS reduction with treatment exceeds 125% of the reduction with sham, using a Student t-test in the intention-to-treat population; men who chose another treatment before the 3-month visit were counted as failures with their baseline value carried forward.[2] The primary safety endpoint was a composite of device-related serious complications at 3 months (new retention lasting more than 21 days, rectourethral fistula, or rectal or gastrointestinal perforation) with a performance goal of 12% or less.[3]
After unblinding, 53 of the 61 control men requalified and elected treatment within 3 to 6 months of enrollment. Treatment and crossover men were followed at 3, 6 and 12 months and then yearly to 5 years, with adverse events adjudicated by independent data-monitoring and clinical-events committees. A man retreated for BPH, medically or surgically, left follow-up.[2]
Results
In the intention-to-treat population, IPSS changed by −11.2 ± 7.6 with water vapor therapy and −4.3 ± 6.9 with sham (p < 0.0001); the registry's 95% confidence intervals for the two group means are −12.5 to −9.9 and −6.1 to −2.5.[1][3] The Cochrane review calculated a mean difference of −6.9 (95% CI −9.06 to −4.74; 195 men) and graded the certainty low for symptom score, because of performance bias and an interval that crosses the 5-point minimal important difference, and moderate for quality of life.[4] A 30% or greater IPSS reduction at 3 months occurred in 106/136 (77.9%) treated men and 21/61 (34.4%) sham men.[1] The composite serious-complication endpoint occurred in 1/136 treated men, within the 12% performance goal.[3][5] In the treatment arm, IPSS fell from a baseline of 22 to 18.6 at 2 weeks (p = 0.0006) and by 50% or more at 3, 6 and 12 months (p < 0.0001), and peak flow rose by 6.2 mL/s at 3 months and stayed up through 12 months.[1]
The sham comparison ended at 3 months, so later reports describe treatment-arm and crossover follow-up without a concurrent control. At 24 months the treatment-arm IPSS was 51% below baseline, and 84% and 74% of treated men had a decrease of at least 5 and at least 8 points.[6] At 3 years the 50% or greater improvements in IPSS, quality of life, peak flow and BPH Impact Index were maintained and surgical retreatment was 4.4%.[7] At 4 years in the original treatment arm, IPSS, quality of life, peak flow and BPH Impact Index had improved by 47%, 43%, 50% and 52% (90 paired men for IPSS, quality of life and BPH Impact Index; 81 for peak flow), with 4.4% surgical retreatment (6/135); the 53 crossover men had 3-year follow-up.[8]
In the final report, 77 of 135 treated men were evaluated at 5 years. Mean IPSS change was −11.1 ± 7.8 from a baseline of 22.0 (reported as near 48%), the IPSS quality-of-life score fell from 4.4 ± 1.1 to 2.2 ± 1.4 (45%), peak flow rose from 9.9 ± 2.2 to 14.0 ± 5.4 mL/s and the BPH Impact Index was 2.2 ± 1.4. The text gives 49% for peak flow and 45% for the BPH Impact Index, where the abstract gives 44% and 48%. Of the 135 treated men, 82 (61%) were both free from retreatment and had a 30% or greater IPSS reduction at 5 years.[2]
Cumulative surgical retreatment in the treatment arm was 2.2% at 12 months, 3.7% at 24 months and 4.4% (6/135) from 36 months on; 83% of surgical retreatments occurred in the first 2 years and none after year 3. Four of the 6 men had obstructive median tissue that was left untreated at the index procedure. A further 11.1% started BPH medication through 5 years. In the crossover group, 4 men had surgery (3 for previously untreated obstructive median tissue) and 10 started medication.[2]
No device- or procedure-related de novo erectile dysfunction occurred. In the sexual-function report, IIEF erectile function and MSHQ-EjD function scores in the treatment arm did not differ from control at 3 months or from baseline at 1 year, the ejaculatory bother score improved 31% over baseline (p = 0.0011), and 32% of treated men at 3 months and 27% at 1 year reached the minimal clinically important difference in erectile function.[9] At 5 years, IIEF erectile function and MSHQ-EjD function changed by −2.4 ± 9.2 and −2.0 ± 3.9, which the authors attribute to aging of the cohort.[2] A post hoc analysis of 125 sexually active men (67 remaining at year 5) found an IIEF erectile-function change of −2.4 ± 8.9 (p = 0.1414) in men without baseline erectile or ejaculatory dysfunction, −3.0 ± 10.1 (p = 0.1259) with a baseline erectile dysfunction history and −4.1 ± 9.2 (p = 0.0127) with a baseline ejaculatory dysfunction history. MSHQ-EjD function fell by −1.6 ± 3.2 (p = 0.0083) in men without baseline dysfunction, and bother scores did not change significantly in any subgroup.[10]
Surgery and treatment delivery
Radiofrequency energy converts sterile water to vapor (103 °C), which a transurethral needle injects into the transition zone of the lateral lobes or into the central zone to treat an obstructive middle lobe. Each injection lasts 9 seconds, and the number of injections depends on prostate size and whether median tissue is treated.[2][9] Treatment-arm men received 4.5 ± 1.8 injections and crossover men 5.1 ± 1.9. The median lobe was treated in 58 of 188 men (30.9%) with 1.6 ± 0.7 additional injections.[2] Mean procedure time, insertion to removal, was 5.3 ± 3.5 minutes in the treatment arm and 4.4 ± 1.7 minutes in the crossover group. All treatments were done in an office or ambulatory surgery center: oral pain medication in 170 of 188 men (90.4%), a prostate block or epidural in 39 (20.7%) and intravenous sedation in 19 (10.1%).[2]
Of the randomized comparison, 122/135 treated men (90.4%) and 12/61 sham men (19.7%) were catheterized before discharge. Mean catheter time was 3.4 ± 3.2 days (N = 123) with treatment and 0.9 ± 0.8 days (N = 12) with sham, and 83 of the 122 catheterized treated men (68%) were catheterized at physician discretion. Four men with a treated median lobe were recatheterized for retention for an average of 5 days.[11]
Adverse events
Through 3 months, the Cochrane review counted Clavien–Dindo grade III–V events in 7/136 (5.1%) treated men and 0/61 sham men (risk ratio 6.79, 95% CI 0.39–117.00, very low-certainty evidence). Grade I–II events were more frequent with treatment (risk ratio 1.89, 95% CI 1.15–3.11), as was an indwelling catheter (risk ratio 35.58, 95% CI 15.37–82.36).[4]
In the final report, device- or procedure-related events were dysuria (16.9% of the treatment arm), gross hematuria (12.5%), hematospermia (7.4%), urinary frequency (5.9%), acute urinary retention (4.4%), suspected urinary infection (3.7%) and decreased ejaculatory volume (3.7%); the crossover group had 18.9%, 11.3%, 3.8%, 5.7%, 5.7%, 7.5% and 7.5%. These were mild to moderate and resolved spontaneously or with routine treatment. There were 151 related events in 53 treatment-arm men and 59 in 23 crossover men, no late related events in years 1 to 5 and no withdrawal attributed to a related event.[2]
The manufacturer's table of adjudicated related events through 4 years in treatment and crossover men (data through February 9, 2019) lists dysuria 17%, gross hematuria 12%, urinary retention 5%, decreased ejaculatory volume 5% (33% resolved), anejaculation 3% (none resolved), worsening erectile dysfunction 2% (none resolved), suspected urinary infection 5%, culture-proven infection 3% and urethral stricture 2%. Six serious events occurred in 4 men: prolonged retention from an untreated intravesical lobe, an allergic reaction to a sedative, bladder neck contracture with bladder stones, and urosepsis after cystoscopy. Of treatment and crossover men, 57% had no related event, 80% of events occurred within 30 days and 89% had resolved. Nine of 188 men (5%) sought other treatment within 4 years.[11]
Limitations
The randomized sham comparison ended at 3 months, when 53 of 61 controls crossed over, so the 5-year results are uncontrolled treatment-arm data. The Cochrane review found only short-term data from this one industry-sponsored trial, and the registry names Boston Scientific as the responsible organization.[2][3][4]
Attrition was substantial: 77 of 135 treatment-arm men (57%) were evaluated at 5 years, and follow-up ended at retreatment, so late means describe men who had not been retreated.[2] The investigators note the absence of urodynamic testing.[2] The sexual-function analyses were limited to sexually active men, which the Cochrane review rated high risk of bias, and the 5-year analysis was post hoc.[4][10] Eligibility excluded prior prostate intervention, recent retention and prostates over 80 cc.[3]
In conversation
- Parallel to L.I.F.T. (2013). Sham-controlled pivotal trial of another office MIST in 30–80 cc prostates; the final Rezūm report cites L.I.F.T.'s 13.6% five-year surgical retreatment.
Same setting PINNACLE (2023)
The final report compares the 4.4% surgical retreatment with 13.6% in the 5-year L.I.F.T. study and with 5-year surgical retreatment of 14% to 51% for TUNA and 8.9% to 21% for TUMT.[2] Those are cross-trial figures, and Rezūm II separately counts 11.1% starting BPH medication.[2] The Cochrane review found no study comparing water vapor therapy with another active treatment; the EAU guideline cites a single-center randomized trial in which bipolar TURP gave greater IPSS, peak flow and postvoid residual improvement at 24 months.[4][12]
Guidelines and approvals
- AUA (Management of LUTS Attributed to BPH, 2026), statement 46. Clinicians should offer water vapor thermal therapy as an option for patients with prostates of 30–80 cc . The supporting text describes IPSS and quality-of-life improvements that remain durable from 3 months through 5 years in appropriately selected patients, and advises that use in prostates up to 150 cc under the expanded FDA indication be reserved for appropriate patients and experienced clinicians.[13]
- EAU (Non-Neurogenic Male LUTS, March 2026). Water vapor thermal therapy is listed among alternative ablative techniques under investigation without a recommendation; the text summarizes this 197-man trial and a 4.4% surgical retreatment rate over 5 years.[12]
- FDA. The 510(k) K150786 substantial-equivalence decision (August 27, 2015; letter corrected September 12, 2016) cleared the Rezūm System for men aged 50 or older with a prostate volume of 30–80 cm³, including hyperplasia of the central zone or a median lobe; its summary cites the Rezūm II randomized placebo-controlled trial (136 treatment, 61 control).[5] The June 11, 2025 clearance (K250584) indicates the system for men aged 50 or older with a prostate volume of 30–150 cm³.[14]
Report history
| Published | Report | Cutoff | Headline results | Citation |
|---|---|---|---|---|
| 2015 | Initial randomized report · primary | — | Change in IPSS from baseline at 3 months (mean ± SD; mean difference is treatment minus sham): −11.2 ± 7.6 vs −4.3 ± 6.9; difference -6.9; CI -9.06–-4.74; P <0.0001 Met Composite at 3 months: new severe retention lasting more than 21 days, rectourethral fistula, or rectal or gastrointestinal perforation (treatment arm only): 1/136; — Met 30% or greater IPSS reduction from baseline at 3 months: 106/136 (77.9%) vs 21/61 (34.4%); — Treatment-arm mean IPSS at 2 weeks (baseline 22): 18.6; P 0.0006 Treatment-arm change in peak flow rate at 3 months: +6.2 mL/s; P <0.0001 | McVary KT, Gange SN, Gittelman MC, et al. Minimally invasive prostate convective water vapor energy ablation: a multicenter, randomized, controlled study for the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia. *J Urol.* 2016;195(5):1529-1538. doi:10.1016/j.juro.2015.10.181 DOI |
| 2016 | Erectile and ejaculatory function · secondary | — | IIEF erectile function and MSHQ-EjD function scores, treatment arm: not different from control at 3 months or from baseline at 1 year; — Improvement in the ejaculatory bother score over baseline: 31%; P 0.0011 Treated men reaching the minimal clinically important difference in erectile function score: 32% at 3 months; 27% at 1 year; — IPSS and peak flow rate versus control: superior to control at 3 months and throughout 1 year; P <0.0001 | McVary KT, Gange SN, Gittelman MC, et al. Erectile and ejaculatory function preserved with convective water vapor energy treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia: randomized controlled study. *J Sex Med.* 2016;13(6):924-933. doi:10.1016/j.jsxm.2016.03.372 DOI |
| 2016 | 2-year report · updated | — | IPSS reduction from baseline at 24 months, treatment arm: 51%; P <0.0001 Treated men with an IPSS decrease of 5 points or more and of 8 points or more at 24 months: 84% and 74%; — Symptoms, flow rate and quality of life after thermal therapy versus after the control procedure, crossover subjects: improved; P 0.024 to <0.0001 | Roehrborn CG, Gange SN, Gittelman MC, et al. Convective thermal therapy: durable 2-year results of randomized controlled and prospective crossover studies for treatment of lower urinary tract symptoms due to benign prostatic hyperplasia. *J Urol.* 2017;197(6):1507-1516. doi:10.1016/j.juro.2016.12.045 DOI |
| 2017 | 3-year report · updated | — | Treatment-arm improvement at 3 years in IPSS, quality of life, Qmax and BPH Impact Index: 50%, 49%, 39% and 57%, respectively; P <0.0001 Surgical retreatment over 3 years: 4.4%; — | McVary KT, Roehrborn CG. Three-year outcomes of the prospective, randomized controlled Rezūm system study: convective radiofrequency thermal therapy for treatment of lower urinary tract symptoms due to benign prostatic hyperplasia. *Urology.* 2018;111:1-9. doi:10.1016/j.urology.2017.10.023 DOI |
| 2019 | 4-year report · updated | — | Improvement at 4 years: IPSS, quality of life, Qmax and BPH Impact Index: 47%, 43%, 50% and 52%; P <0.0001 Surgical retreatment over 4 years: 4.4%; — | McVary KT, Rogers T, Roehrborn CG. Rezūm water vapor thermal therapy for lower urinary tract symptoms associated with benign prostatic hyperplasia: 4-year results from randomized controlled study. *Urology.* 2019;126:171-179. doi:10.1016/j.urology.2018.12.041 DOI |
| 2021 | Final 5-year report · updated | — | Treatment-arm mean IPSS change from baseline (22.0) at 5 years, per-protocol: −11.1 ± 7.8; — Treatment-arm mean IPSS quality-of-life score at 5 years (baseline 4.4 ± 1.1): 2.2 ± 1.4; — Treatment-arm mean peak flow rate at 5 years (baseline 9.9 ± 2.2 mL/s): 14.0 ± 5.4 mL/s; — Treatment-arm mean BPH Impact Index at 5 years: 2.2 ± 1.4; — Cumulative surgical retreatment through 5 years, treatment arm: 6/135 (4.4%); — Retreatment through 5 years in the 53 crossover men: 4 surgical, 10 BPH medication; — Treatment-arm men both free from retreatment and with a 30% or greater IPSS reduction at 5 years: 82/135 (61%); — Change in IIEF erectile function and MSHQ-EjD function domains at 5 years, treatment arm: −2.4 ± 9.2 and −2.0 ± 3.9; — | McVary KT, Gittelman MC, Goldberg KA, et al. Final 5-year outcomes of the multicenter randomized sham-controlled trial of a water vapor thermal therapy for treatment of moderate to severe lower urinary tract symptoms secondary to benign prostatic hyperplasia. *J Urol.* 2021;206(3):715-724. doi:10.1097/JU.0000000000001778 DOI |
| 2021-10-30 | 5-year sexual function · post-hoc | — | IIEF erectile function change over 5 years, no baseline ED or EjD (n = 32 paired at 5 years): −2.4 ± 8.9; P 0.1414 IIEF erectile function change over 5 years, baseline ED history (n = 28 paired at 5 years): −3.0 ± 10.1; P 0.1259 IIEF erectile function change over 5 years, baseline EjD history (n = 17 paired at 5 years): −4.1 ± 9.2; P 0.0127 MSHQ-EjD function change over 5 years, no baseline ED or EjD (n = 31 paired at 5 years): −1.6 ± 3.2; P 0.0083 MSHQ-EjD function change over 5 years, baseline ED history (n = 28 paired at 5 years): −2.3 ± 4.7; P 0.0158 MSHQ-EjD function change over 5 years, baseline EjD history (n = 16 paired at 5 years): −1.6 ± 4.8; P 0.1970 | McVary KT, El-Arabi A, Roehrborn C. Preservation of sexual function 5 years after water vapor thermal therapy for benign prostatic hyperplasia. *Sex Med.* 2021;9(6):100454. doi:10.1016/j.esxm.2021.100454 DOI |
References
1. McVary KT, Gange SN, Gittelman MC, et al. "Minimally invasive prostate convective water vapor energy ablation: a multicenter, randomized, controlled study for the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia." J Urol. 2016;195(5):1529-1538. doi:10.1016/j.juro.2015.10.181
2. McVary KT, Gittelman MC, Goldberg KA, et al. "Final 5-year outcomes of the multicenter randomized sham-controlled trial of a water vapor thermal therapy for treatment of moderate to severe lower urinary tract symptoms secondary to benign prostatic hyperplasia." J Urol. 2021;206(3):715-724. doi:10.1097/JU.0000000000001778
3. Boston Scientific Corporation. "Safety and Efficacy Study for the Treatment of BPH (Enlarged Prostate): Rezūm II." ClinicalTrials.gov identifier NCT01912339, results record. clinicaltrials.gov/study/NCT01912339
4. Kang TW, Jung JH, Hwang EC, et al. "Convective radiofrequency water vapour thermal therapy for lower urinary tract symptoms in men with benign prostatic hyperplasia." Cochrane Database Syst Rev. 2020;3:CD013251. doi:10.1002/14651858.CD013251.pub2
5. US Food and Drug Administration. "510(k) K150786: Rezūm System (NxThera), decision letter and 510(k) summary." accessdata.fda.gov/cdrh_docs/pdf15/K150786.pdf
6. Roehrborn CG, Gange SN, Gittelman MC, et al. "Convective thermal therapy: durable 2-year results of randomized controlled and prospective crossover studies for treatment of lower urinary tract symptoms due to benign prostatic hyperplasia." J Urol. 2017;197(6):1507-1516. doi:10.1016/j.juro.2016.12.045
7. McVary KT, Roehrborn CG. "Three-year outcomes of the prospective, randomized controlled Rezūm system study: convective radiofrequency thermal therapy for treatment of lower urinary tract symptoms due to benign prostatic hyperplasia." Urology. 2018;111:1-9. doi:10.1016/j.urology.2017.10.023
8. McVary KT, Rogers T, Roehrborn CG. "Rezūm water vapor thermal therapy for lower urinary tract symptoms associated with benign prostatic hyperplasia: 4-year results from randomized controlled study." Urology. 2019;126:171-179. doi:10.1016/j.urology.2018.12.041
9. McVary KT, Gange SN, Gittelman MC, et al. "Erectile and ejaculatory function preserved with convective water vapor energy treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia: randomized controlled study." J Sex Med. 2016;13(6):924-933. doi:10.1016/j.jsxm.2016.03.372
10. McVary KT, El-Arabi A, Roehrborn C. "Preservation of sexual function 5 years after water vapor thermal therapy for benign prostatic hyperplasia." Sex Med. 2021;9(6):100454. doi:10.1016/j.esxm.2021.100454
11. Boston Scientific. Rezūm Delivery Device Kit for BPH: Directions for Use, 51344625-01 Rev. A (2021, Canada edition), pivotal clinical study summary. Manufacturer document.
12. European Association of Urology. EAU Guidelines on Management of Non-neurogenic Male Lower Urinary Tract Symptoms (LUTS). March 2026 update, section 5.3.4.c.1.
13. Goueli R, Badlani GH, Welliver C, et al. "Management of lower urinary tract symptoms attributed to benign prostatic hyperplasia: AUA guideline (2026)." American Urological Association; approved April 2026.
14. US Food and Drug Administration. "510(k) K250584: Rezum System, decision letter and indications for use," June 11, 2025. accessdata.fda.gov/cdrh_docs/pdf25/K250584.pdf