Injection density in Rezūm®: Less might not be more. A multicentric international study

Water Vapor Thermal Therapy (WVTT) has emerged as a minimally invasive surgical therapy (MIST) for benign prostatic obstruction. However, the optimal number of intraprostatic injections remains debated. This study introduces injection density (ID), defined as the number of injections per 10 cc of prostate volume, to assess its impact on treatment failure after WVTT.

Multicentric retrospective study across 11 European centers, analysing patients who underwent WVTT between March 2019 and March 2024. Baseline, surgical, and postoperative data were collected during a 24 months follow-up. The primary outcome was treatment failure, defined as the need for medical or surgical intervention 12 months post-WVTT. Secondary outcomes included sexual function and postoperative complications. Logistic regression was performed across ID cut-off points from 0.75 to 2.5 injections per 10 cc.

A total of 722 patients underwent WVTT with a mean age of 64 years and a mean prostate volume of 60 cc. Baseline Qmax was 8.0±3.6mL/s. Intermediate ID cut-off points (1.25-1.75) suggested a protective effect against treatment failure, with 1.75 being the first to reach statistical significance (P=.028). Higher ID cut-off points (2.00-2.50) maintained a protective effect, but only 2.25 reached significance (P=.024). No significant relationship was found between ID and complications. Sexual function remained stable across ID thresholds.

Optimizing ID during WVTT may improve success rates without increasing complications or negatively impacting sexual function. These findings support a volumetric approach over the traditional linear injection technique to enhance WVTT outcomes.