Convective water vapor ablation successful at 2 years

San Diego-A treatment system that uses steam to ablate prostate tissue (Rezum, NxThera, Inc.) can be considered as a first-line therapy for the treatment of lower urinary tract symptoms (LUTS) secondary to BPH, say investigators from a non-randomized multicenter pilot study with 2-year duration of successful outcomes.

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Durable improvements in urinary symptoms, peak urinary flow (Qmax), and quality of life were realized in men treated with convective water vapor ablation with no adverse effects on sexual function, reported Christopher Dixon, MD, at the AUA annual meeting in San Diego. 

“All of the clinical parameters in this pilot study were improved and durable, in a very clinically significant way,” said Dr. Dixon, a practicing urologist in New York. “In my opinion as a clinical urologist with an academic background and a lot of experience with medical management of BPH, given the overall clinical database with it, I think it is very reasonable to consider this as a first-line therapy for men with clinical BPH.”

The technology used in the study is an office-based transurethral needle ablation (TUNA) procedure based on phase change convective heating, which involves radiofrequency to convert sterile water into steam, and injecting that steam in a controlled fashion into the transition zone to ablate tissue rapidly and efficiently.

Next: "The anatomy is ideally suited to convective therapy"

“The thermodynamics of this process are extremely efficient; the anatomy is ideally suited to convective therapy,” Dr. Dixon said.

In contrast to conductive heating (as with Prostiva and TUMT), convective heating respects tissue boundaries, thereby leaving the peripheral zone and the urethra intact, he noted.

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“Vapor disperses within the transition zone but stays within the boundaries of the transition zone. This is because of the thermodynamic and physical principles of convective heating; it will not exit the transition zone,” Dr. Dixon said.

The components of the Rezum system are a water vapor generator and a modified cystoscope to deliver the steam. A series of one to three injections, each lasting about 9 seconds, is delivered into the transition zone on either side of the urethra, and is dispersed through the tissue interstices. The thermal energy denatures the cell membranes, causing instant cell death. In addition, because vapor is wet thermal energy, there is no charring, dessication, or carbonization of the treated tissue. Median lobes can be targeted effectively.

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Two-year data from the first 65 patients to be treated with the system were presented at the AUA annual meeting. Patients had moderate to severe symptoms and were treated at three centers in the Dominican Republic, Czech Republic, and Sweden. To be eligible, patients had to have an International Prostate Symptom Score (IPSS) ≥13, Qmax ≤15 mL/s, postvoid residual volume <300 mL, and a prostate volume of 20 to 120 cc as measured by transrectal ultrasound. Patients with a median lobe could be enrolled.

At baseline, the mean IPSS was 21.7, the mean prostate volume was 49 cc, and the mean serum PSA level was 3.9 ng/mL.

Next: IPSS improvement seen

IPSS improvement seen

Forty-three of 65 patients (66%) had follow-up to 2 years. Their IPSS improved from 21.7 at baseline to 9.6 at 2 years, for a mean decrease of 12.1 points (p<.001). Some 61% of patients with 2-year follow-up data had a ≥50% improvement in IPSS, and 79% had a ≥5-point (moderate to marked) improvement.

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As expected with an improvement in symptoms, quality of life scores improved as well, from a mean of 4.4 at baseline to a mean of 1.7 at 2 years (p<.001), corresponding to a 58% improvement. The Benign Prostatic Hyperplasia Impact Index improved from 7.1 at baseline to 2.3 at 2 years (p<.001).

The improvement in flow rate was sustained through 2 years. Qmax increased from 8.3 mL/s at baseline to 12.0 mL/s at 2 years, corresponding to a 56% improvement (p<.001).

The improvements in IPSS and mean flow rates in the pilot study were consistent with those observed in the pivotal trial, a multicenter, randomized, blinded, controlled study that served as the basis for FDA clearance, Dr. Dixon noted.

Adverse events were mild to moderate, consistent with routine endoscopic procedures and/or LUTS, and generally transient. There was no de novo erectile dysfunction and no apparent effect on ejaculation. No new adverse events were seen between year 1 and year 2.

Dr. Dixon is a consultant/adviser for NxThera. Several of his co-authors are investigators and one co-author is a consultant/investigator for NxThera.

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