Prostate MRI Transitional Zone Volume Predicts BPH Enucleation Volume Better than Alternative Modalities

<b><i>Introduction:</i></b> Guidelines for benign prostate hyperplasia (BPH) interventions are volume based. The degree to which different imaging modalities actually correlate to treated volume is not known for BPH. The present study compares the accuracy of preoperative ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and MRI-transitional zone (TZ) to BPH enucleation weight. <b><i>Methods:</i></b> A retrospective review of patients who underwent enucleation for BPH and had preoperative transrectal ultrasound (TRUS), CT, and/or MRI was performed. Total prostate volumes were measured for CT, MRI, and TRUS; MRI-TZ volume was also measured. The primary outcome was difference between enucleated pathology weight in grams and preoperative imaging volume. Differences between enucleation and imaging volume for each modality were calculated with one-way analysis of variance, with Tukey's honest significance test to determine pairwise significance (RStudio V1.2). <b><i>Results:</i></b> From January to October 2020, there were 114 preoperative imaging studies available for 95 patients. Thirty-four (30%) of the studies were TRUS, 46 (40%) were CT, and 34 (30%) were MRI. MRI-TZ most accurately predicted enucleation volume on multivariate analysis (F-statistic <i>p</i>-value < 0.001). Preoperative imaging was greater than enucleation volume by a median of 46 cc for TRUS, 51 cc for CT, 53 cc for MRI, and 14 cc for MRI-TZ. Pairwise significance was reached for MRI-TZ over CT (<i>p</i>-adj < 0.001), MRI-TZ over MRI (<i>p</i>-adj < 0.001) and MRI-TZ over US (<i>p</i>-adj = 0.03). <b><i>Conclusions:</i></b> Enucleation volume for BPH was most accurately predicted by TZ volume on MRI compared with total prostate volume on CT, TRUS, and MRI. MRI total volume was not superior to CT total volume. Focusing on MRI-TZ volume rather than total prostate volume may more accurately stratify patients for BPH treatment. In experienced hands, median enucleation volume is within 14 cc of MRI-TZ volume.