Prostatic artery embolization with polyethylene glycol microspheres: evaluation in a canine spontaneous benign prostatic hyperplasia model

Canine Prostate Cancer: Current Treatments and the Role of Interventional Oncology

Prostate carcinoma is one of the most common cancers worldwide in men, with over 3 million men currently living with prostate carcinoma. In men, routine screening and successful treatment schemes, including radiation, prostatectomy, or hormone therapy, have allowed for high survivability. Dogs are recognized as one of the only mammals to spontaneously develop prostate neoplasia and are an important translational model. Within veterinary medicine, treatment options have historically been limited in efficacy or paired with high morbidity. Recently, less invasive treatment modalities have been investigated in dogs and people and demonstrated promise. Below, current treatment options available in dogs and people are reviewed, as well as a discussion of current and future trends within interventional treatment for canine PC.

Prostatic artery occlusion: initial findings on pathophysiological response in a canine prostate model

Background

Prostatic artery embolization (PAE) is an alternative treatment for symptomatic benign prostatic hyperplasia (BPH) in men. A technical modification of conventional PAE has been developed in a canine prostate model consisting of prostatic artery occlusion (PAO) using Onyx^® whose therapeutic effect is prostate shrinkage. However, the underlying mechanisms are not well clarified. The purpose was to evaluate the biological mechanisms responsible for therapeutic effects of PAO in the canine prostate.

Methods

Ten adult male beagles (5.0±0.82 years) underwent PAO with Onyx-18 (n=7) and prostatic artery angiography as control (n=3). Blood samples were taken at different time points of follow-up (baseline, 1 week, 2 weeks, 1 month, 3 months and 6 months) to measure the serum canine prostate specific esterase (CPSE). MRI examinations were also performed to document the prostate volume (PV) before and after interventions at different time points of follow-up. Prostates were harvested at 2 weeks (n=2) in the PAO-group, and the remaining ones (n=8) at 6 months for the determinations of intraprostatic testosterone and dihydrotestosterone (DHT) by ELISA, apoptosis by TUNEL assay and histopathological study.

Results

The mean serum CPSE concentration started to decrease significantly from 2 weeks to 6 months after PAO along with PV compared with baseline data. In addition, a moderate but significant correlation was observed between CPSE and PV (r=0.655, P=0.000). Regarding intraprostatic androgens, testosterone was significantly higher after PAO than control (19.70 vs. 4.87 ng/mL, P=0.002), whereas DHT was lower but no significant (112.52 vs. 138.35 pg/mL, P=0.144). In histological study, PAO induced a severe hemorrhagic necrosis in the whole prostates along with inflammatory cell infiltration at early 2 weeks, and then diffuse interstitial fibrosis with atrophy of the glandular epithelium and intraprostatic cavity formation at 6 months. Apoptosis was detected in all specimens with higher apoptotic index after PAO at 2 weeks (7.35%) and at 6 months (4.38%) compared with control (2.64%), without statistically significant difference between groups.

Conclusions

PAO induces hemorrhagic ischemia predominantly resulting in necrosis rather than apoptosis with prostate shrinkage. CPSE is a potential biomarker to assess the response to PAO in the canine prostate.

Prostatic artery occlusion versus prostatic artery embolisation for the management of benign prostatic hyperplasia: early results in a canine model

OBJECTIVE

To compare the technical efficacy and safety between prostatic artery occlusion (PAO) with ethylene vinyl alcohol copolymer (EVOH) and prostatic artery embolizsation (PAE) with microspheres in a canine model.

METHODS

17 adult male beagles underwent PAO (n = 7) with Onyx-18 or PAE (n = 10) with microspheres (300-500 µm). To evaluate the primary outcomes (technical efficacy and safety), MRI evaluations were performed immediately before and 1 week, 2 weeks, and 1 month after procedures to document prostate volume (PV); and all dogs were inspected for procedure-related complications during 1 month follow-up. The secondary outcomes included the prostate ischaemia size detected by MRI and recanalisation of prostatic artery by follow-up angiography. Differences between groups were statistically analysed.

RESULTS

Both procedures were bilaterally successful in all animals. Compared with PAE, the mean fluoroscopy time (23.80 vs 36.24 min, p = 0.014) and radiation dose (68.19 vs 125.26 mGy, p = 0.003) were significantly less in PAO procedure. The mean percentage of PV change significantly decreased in both groups at 2 weeks (30.71% vs  37.89%) and 1 month (56.41% %vs 55.56%) after PAO and PAE respectively), without significant differences between groups at either time point. No major complications were observed except one animal after PAO with transient haematuria and acute urinary retention. The mean prostate ischaemia induced by PAO was significant greater compared with PAE at 1 week (43.44% vs 18.91%, p=0.001). PAO with EVOH is technically feasible and with comparable efficacy and safety with PAE. There are possible benefits to PAO over PAE.

ADVANCES IN KNOWLEDGE

A new technical modification of the PAE consisting of the use of liquid embolic agent to occlude the prostatic artery trunk and its branches has been developed in pre-clinical study, showing to be an effective and safe procedure which can induce a significant prostate shrinkage for the management of symptomatic benign prostatic hyperplasia in patients. In addition, the findings have showed a similar therapeutic effect comparable with the conventional PAE using microspheres.

Urinary Stent Development and Evaluation Models: In Vitro, Ex Vivo and In Vivo-A European Network of Multidisciplinary Research to Improve Urinary Stents (ENIUS) Initiative

Background: When trying to modify urinary stents, certain pre-clinical steps have to be followed before clinical evaluation in humans. Usually, the process starts as an in silico assessment. The urinary tract is a highly complex, dynamic and variable environment, which makes a computer simulation closely reflecting physiological conditions extremely challenging. Therefore, the pre-clinical evaluation needs to go through further steps of in vitro, ex vivo and in vivo assessments. Methods and materials: Within the European Network of Multidisciplinary Research to Improve Urinary Stents (ENIUS), the authors summarized and evaluated stent assessment models in silico, in vitro, ex vivo and in vivo. The topic and relevant sub-topics were researched in a systematic literature search in Embase, Scope, Web of Science and PubMed. Clinicaltrials.gov was consulted for ongoing trials. Articles were selected systematically according to guidelines with non-relevant, non-complete, and non-English or Spanish language articles excluded. Results: In the first part of this paper, we critically evaluate in vitro stent assessment models used over the last five decades, outlining briefly their strengths and weaknesses. In the second part, we provide a step-by-step guide on what to consider when setting up an ex vivo model for stent evaluation on the example of a biodegradable stent. Lastly, the third part lists and discusses the pros and cons of available animal models for urinary stent evaluation, this being the final step before human trials. Conclusions: We hope that this overview can provide a practical guide and a critical discussion of the experimental pre-clinical evaluation steps needed, which will help interested readers in choosing the right methodology from the start of a stent evaluation process once an in silico assessment has been completed. Only a transparent multidisciplinary approach using the correct methodology will lead to a successful clinical implementation of any new or modified stent.

Prostatic Artery Embolization (PAE) Using Polyethylene Glycol Microspheres: Safety and Efficacy in 81 Patients

PURPOSE

To evaluate the safety and efficacy of prostatic artery embolization (PAE) using polyethylene glycol microspheres (PEGM) in patients with lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH).

MATERIALS AND METHODS

This multicentric prospective study enrolled 81 patients who underwent PAE with 400 ± 75 µm PEGM (HydroPearl®, Terumo, Japan). Results from baseline and 1-, 3-, 6-, and 12-month follow-ups were assessed for subjective outcomes including International Prostate Symptoms Score (IPSS), Quality of life (QoL), and International Index of Erectile Function, and objective outcomes such as peak urinary flow (Qmax) and post-void residual volume (PVR). The visual analogue scale, satisfaction questionnaire, prostatic volume, and prostatic specific antigen levels were also evaluated. Complications were documented using the modified Clavien-Dindo classification.

RESULTS

Technical success was obtained in all patients. Clinical success was achieved in 78.5% of patients. Before PAE, 54.3% of patients had an indwelling catheter which was removed in 75% of them after procedure. A statistically significant decrease was observed in IPSS and QoL from baseline to 12 months (20.14 vs 5.89; 4.8 vs 0.63, P < .01), respectively. Objective outcomes also showed a statistically significant improvement in Qmax (+ 114.9%; P < .01), achieving a maximum urinary flow of 14.2 mL/sec, and PVR (decrease 58%; P < .05) at 12 months. Minor complications (Clavien-Dindo grades I-II) occurred in 13.6% of patients, without major complications observed.

CONCLUSION

PAE with PEGM is safe and effective treatment in patients with symptomatic BPH, with a significant improvement in both subjective and objective outcomes.