Laboratory investigation: Resorbable microsphere for transient uterine artery occlusion

Researchers from France have recently developed a new kind of embolic, one that aims to ensure full and constant recanalization of the embolized artery. The most widely used embolics at this time degrade over several months, inciting chronic changes in the embolized vessel and organ. Previous animal models have shown that even after partial recanalization of the uterine artery, both fertility and birthweight are lowered. Remodeling of vessel walls can inhibit important dilatation of the uterine artery that occurs during pregnancy. A resorbable microsphere would occlude the vessel for a short time and achieve ischemia of a fibroid, but would subsequently be completely eliminated before the onset of a chronic response.

To show this, the authors embolized the uterine arteries of sheep using either their newly designed resorbable microspheres comprised of trisacryl-gelatin or traditional nonresorbable microspheres. At 7 days after embolization, an angiogram was performed to evaluate vascularity and the sheep were sacrificed to allow histologic evaluation of their arteries and uteri.

The study found that the resorbable microspheres disappeared and the arteries recanalized within 7 days in all of the sheep, something that was observed in only half of uterine arteries embolized with nonresorbable microspheres. Changes to the uterine tissue were observed to be similar. This exciting technology is yet to be tested in a large cohort, in a fibroid uterus, or in a human.


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Example of full UA recanalization and complete parenchyma opacification after embolization with REM. (a) Angiogram obtained before embolization. UA (arrow) and parenchyma (star) are opacified. (b) Angiogram obtained 10 minutes after embolization. Flow is interrupted at the level of the descending UA (arrow). (c) Angiogram obtained 7 days after embolization. Opacification of UA and its branches (arrow) at arterial phase. (d) Angiogram obtained 7 days after embolization. Opacification of parenchyma (star).


Citation:  Verret, V. et al. A Novel Resorbable Embolization Microsphere for Transient Uterine Artery Occlusion: A Comparative Study with Trisacryl-Gelatin Microspheres in the Sheep Model. Journal of Vascular and Interventional Radiology (2014)


Post author: Amish Patel, MD

Radiofrequency ablation of renal cell carcinomas: outcomes and predictors of efficacy

With the incidence of RCC on the rise, ablative techniques have become more commonplace. However, the existing body of literature is limited by studies that are small in size, have varied ablative techniques, or lack pathology of the lesion (benign vs. malignant). By retrospectively evaluating 100 path-proven RCCs treated with percutaneous RFA only, researchers at UCLA have aimed to better understand predictors of successful treatment and outcomes of RF ablation of RCCs.

By using the RENAL nephrometry score, a tool for standardizing the description of renal masses, the authors sought to determine which tumor characteristics were most predictive of treatment success. This tool is comprised of five components, Radius, Exophytic/Endophytic, Nearness of tumor to collecting system or sinus, Anterior/Posterior, and Location relative to polar lines. The authors found that the overall RENAL score predicted the ability to achieve complete tumor ablation after one session with no evidence of local tumor progression on follow-up imaging. Of the RENAL score components, Radius (size) and Location correlated with successful outcome.

At a follow-up of 2.1 years, the authors found an overall 95% success rate in treating these tumors, although 9% of tumors required a second ablation to obtain a complete response. 98.7% of patients remained free of metastasis and no patient died as result of their RCC, figures which are consistent with existing data. Although other ablative techniques are gaining popularity, RF remains the most proven modality for the treatment of renal cell carcinoma.


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USEFUL LINK: RENAL Nephrometry Score Calculator (http://www.nephrometry.com)


Citation: McClure, T. D. et al. Intermediate Outcomes and Predictors of Efficacy in the Radiofrequency Ablation of 100 Pathologically Proven Renal Cell Carcinomas. Journal of Vascular and Interventional Radiology (2014).


Post author: Amish Patel, MD

Researchers investigate new methods for dose quantification following Y-90 using PET/CT

Hepatocellular carcinoma is often managed using a lobar arterial injection of Yttrium-90 radioembolization therapy. This study describes the use of PET-CT to localize and quantify the dose after glass microsphere Y-90 therapy. This retrospective single institution study looked at 64 post-radioembolization “dose maps” created from reconstructed PET-CT images. Contouring of the liver parenchyma and tumors (using pre-procedure imaging if needed) was performed and aligned with these dose maps. A total of 113 tumors were evaluated with an average size of 4.8 cm ±4. The average tumor dose was 173 Gy ±109 and the average non-tumor liver parenchyma dose was 93.4 Gy ±32.6. The calculated average tumor-to-parenchyma dose ratio was 2.2, which suggested a preferential Y-90 uptake within the tumors.

Comments:

The authors were able to characterize the dose deposition of Y-90 in a large cohort of HCC patients being treated using the recommended dose administration algorithms. The study quantifies the well-known, extremely heterogeneous microsphere deposition and highlights the error of applying broad dosing guidelines to all patients. This imaging technique is a valuable tool for any study looking to optimize dosing and clinical response and should be considered for future research studies evaluating the wide discrepancies between dosing and deposition.


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Citation:  Lea WB, Tapp KN, Tann M, et al. Microsphere Localization and Dose Quantification Using Positron Emission Tomography/CT following Hepatic Intraarterial Radioembolization with Yttrium-90 in Patients with Advanced Hepatocellular Carcinoma. J Vasc Interv Radiol (2014)


Post author: Nicholas Hendricks, MD

Minimally invasive therapy for prostate enlargement provides alternative to surgical or endoscopic treatment

Benign prostatic hyperplasia (BPH) affects as many as 90% of all men aged 70-89 years and leads to over 4 million annual doctor visits resulting in over 1 billion dollars in direct healthcare costs annually. Patients with moderate to severe symptoms related to BPH and in whom medical therapies fail are typically treated with transurethral resection of the prostate (TURP) or prostatectomy.

In 2010, Prostate Artery Embolization (PAE) was first described to diminish blood supply to the prostate and reduce its size. The clinical trials and the science backing PAE are explored in the September edition of the Journal of Vascular and Interventional Radiology. A number of studies reviewed in this JVIR consensus paper validate the efficacy of PAE in reducing urinary symptoms from BPH. When compared in a head-to-head study with TURP, both methods showed similar efficacy, with PAE providing the advantage of less bleeding and lower rates of urinary catheterization. PAE also does not require general anesthesia, imparts little pain, and is associated with minimal blood loss. While the authors note that PAE can be technically challenging to perform, quality of life scores following PAE show that patients are quite satisfied with the symptomatic relief that PAE provides when performed successfully. The authors conclude that current data regarding PAE shows promise.

Comments: 

The present article provides the foundation that PAE appears safe and efficacious based on short-term follow-up and is best performed by an Interventional Radiologist. Further, the SIR supports the performance of high-quality clinical research to expand the numbers of patients studied, to extend the duration of follow-up, and to compare the PAE procedure against existing surgical therapies.


To see the article in its entirety free of charge, click here.


To listen to a JVIR podcastinterview regarding this work, click here or visit JVIR on iTtunes.

(a) Coronal T2-weighted MR image of the prostate demonstrates heterogeneous nodular enlargement of the central gland, with impingement on the bladder neck secondary to median lobe hypertrophy (black arrow). (b) Selective angiography of the left prostatic artery (white arrow) shows an enlarged prostate gland with increased vascularity in the central gland. (c) Coronal reformatted image from cone-beam CT after left prostatic artery injection depicts near-homogenous perfusion of the left hemiprostate (black asterisk), without evidence of potential nontarget embolization. (d) Angiogram after embolization to a target endpoint of near-stasis shows a lack of significant parenchymal perfusion.


Citation:  McWilliams, J. P. et al. Society of Interventional Radiology Position Statement: Prostate Artery Embolization for Treatment of Benign Disease of the Prostate. Journal of Vascular and Interventional Radiology 25, 1349–1351 (2014).


Images: Bagla, S. et al. Early Results from a United States Trial of Prostatic Artery Embolization in the Treatment of Benign Prostatic Hyperplasia. Journal of Vascular and Interventional Radiology 25, 47–52 (2014).


Post author: Austin Bourgeois, MD