Role of Ultrasound Elastography in Patient Selection for Prostatic Artery Embolization
Is baseline ultrasound elastography predictive of prostate artery embolization efficacy?
Take away point
Baseline prostatic elastic modulus and shear wave velocity measurements each predict efficacy of prostate artery embolization at 1 year.
de Assis A.M., Moreira A.M., Carnevale F.C., Marcelino A.S.Z., Antunes A.A., Srougi M., and Cerri G.G. Role of Ultrasound Elastography in Patient Selection for Prostatic Artery Embolization. J Vasc Interv Radiol. 2021 Oct; 32 (10): 1410-1416.
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Prospective, observational, descriptive, single-center cohort study.
No reported funding
Academic setting. University of Sao Paulo Medical School, Sao Paulo, Brazil.
Ultrasound elastography (US-E) has recently been described as a novel tool to evaluate prostate artery embolization (PAE) outcomes with anatomical and functional assessments in patients with benign prostatic hyperplasia (BPH). US-E demonstrated that PAE not only treats bladder outlet obstruction (BOO) by reducing prostate volume, but also by improving the α-adrenergic mediated effect on prostatic muscular tonus, which addresses the dynamic component of BOO. While recent US-E research gave interesting insights on PAE mechanism of action, research on the prognostic role of US-E is lacking.
The authors performed a prospective, observational, descriptive, single-center cohort study involving 20 consecutive patients. Inclusion criteria were lower urinary tract symptoms LUTS) attributed to BPH for at least 6 months refractory to standard medical treatment (α-1 adrenergic receptor antagonist with or without 5-α reductase inhibitor), international prostate symptom score (IPSS) ≥ 8, and prostate volume ≥ 40 cm3 and ≤ 200 cm3. Exclusion criteria were biopsy-confirmed cancer, active urinary infection, presence of urinary retention requiring use of Foley urinary catheter, serum creatinine ≥ 2 mg/dL, and previous pelvic surgery or radiotherapy. From February 2018 to October 2019, 20 patients met inclusion criteria but 2 did not return for follow up and 1 refused to complete evaluation therefore the remaining 17 entered statistical analysis.
Primary endpoints were prostatic elastic modulus (EM) and shear wave velocity (SWV) assessed with US-E up to 30 days before and at 23–37 days after PAE. Patients on α-1 adrenergic antagonist were maintained until after the second US-E evaluation, after which the medication was permanently withdrawn. Secondary endpoints included IPSS questionnaire, IPSS-Quality of Life (QoL) item, and peak urinary flow rate (Qmax) assessed using uroflowmetry, among others. All ultrasound examinations were performed transrectally with an 11C3 endocavity probe (Toshiba Medical Systems Corporation, Otawara, Japan) on a Toshiba Aplio i800 (Toshiba Medical Systems Corporation) utilizing 2-dimensional sound wave elastography (SWE) via acoustic structure quantification and dynamic energy generation via acoustic radiation force impulse that generated multifocal stress and enabled EM and SWV measurement by building colored elastographic maps. This meant the exams did not depend on tissue compression by the operator during examinations. EM and SWV values were obtained from maps including the transitional zone of both lobes of the prostate simultaneously in at least 2 axial slices at the middle third of the prostate. All examinations were performed by the same radiologist (A.S.Z.M.).
Pearson product-moment correlation tests were used to assess association of IPSS at 1 year with baseline EM and SWV. Receiver operating characteristic (ROC) curves were used to determine predictive cutoff values of baseline EM and SWV. PAE efficacy at 1 year was considered optimal at IPSS < 8, QoL < 2, or Qmax ≥ 12 mL/s, respectively. Area under ROC curves were obtained at 95% confidence interval and statistical significance was defined as bicaudal type I error (p) < 0.05.
16 of the 17 patients (94.1%) underwent bilateral PAE. Catheterization was technically unsuccessful in the remaining 1 patient (5.9%) due to atherosclerosis. EM was moderately positively correlated with IPSS at 1 year (R = 0.62) and SWV was slightly more positively correlated with IPSS at 1 year (R =0.68), with both correlations being statistically significant (p = 0.007 and p = 0.002, respectively). SWV was also slightly positively correlated with QoL at 1 year but without statistical significance (p = 0.09, R = 0.41). Baseline EM ≥ 50.14 kPa predicted suboptimal IPSS with 84.6% specificity, suboptimal QoL with 68.8% specificity, and suboptimal Qmax with 80.0% specificity; and baseline SWV ≥ 5.9 m/s predicted suboptimal IPSS with 100% specificity, suboptimal QoL with 81.3% specificity, and suboptimal Qmax with 90.0% specificity. Results consistently demonstrated inferior PAE outcomes for patients with very low initial prostate elasticity, with potential to predict patient suitability for PAE using the possible prognostic cutoff values of EM < 50.14 kPa and/or SWV < 5.9 m/s.
This study (1) further described PAE’s effect on prostate elasticity as measured via EM and SWV, and (2) explored the prognostic value of US-E in categorizing patients as good candidates for PAE by assessing IPSS, QoL, and Qmax at 1 year. A notable advantage to this study was the use of ultrasound that utilized dynamic energy generation via acoustic radiation force impulse, which meant ultrasound exams were not operator dependent.
Zayn Mohamed, JD
MS-4 Doctor of Medicine Candidate,
University of South Florida Morsani College of Medicine