Feasibility of temporary protective embolization of normal liver tissue using degradable starch microspheres during radioembolization of liver tumours

Temporary Flow Diversion in Oncological Embolization Procedures Using Degradable Starch Microspheres

OBJECTIVES

This study aims to report on the application of degradable starch microspheres to provide flow diversion by means of temporary embolization of healthy tissues in oncological endovascular procedures when tumor feeding vessels are not selectively accessible.

METHODS

This is a multicenter retrospective analysis of patients undergoing visceral embolization procedures of malignancies. The inclusion criteria were as follows: flow diversion performed by injection of degradable starch microspheres, visceral embolization procedures with unfeasible superselective catheterism of the target, and a malignant pathology. Technical success was defined as complete flow diversion with temporary exclusion of the non-target district from arterial flow, associated with successful embolization of the target. Clinical success was intended as procedural achievement with patient clinical improvement.

RESULTS

Sixteen patients were included in this analysis. Peripheral embolization procedures were performed in the coeliac visceral district all in oncologic patients, including 4 transarterial radioembolization work-up procedures in patients with hepatocarcinoma, 10 chemioembolization procedures in patients with hepatocarcinoma (8) or cholangiocarcinoma (2), and 2 palliative transarterial embolizations in patients with gastric cancer. Technical success was obtained in 100% of the cases, while clinical success was reached in 87.5%: in two chemioembolization procedures, despite technical success, the procedural clinical benefits were partial, with an incomplete target lesion response. Minor complications occurred in five patients (31.2%).

CONCLUSIONS

In this study, temporary flow diversion with degradable starch microspheres during oncological embolization procedures was safe and effective; this approach is suitable to protect healthy surrounding tissues when vessels feeding the target cannot be selected with the microcatheter.

99mTc/90Y radiolabeled biodegradable gel microspheres for lung shutting fraction assessment and radioembolization in hepatocellular carcinoma theranostics

Transarterial radioembolization (TARE) is a well-established clinical therapy for the treatment of patients with intermediate to advanced hepatocellular carcinoma (HCC) or those who are ineligible for radical treatment. However, commercialized radioactive microspheres still have some issues, such as high density, complicated preparation, non-biodegradability. Furthermore, the use of different radioactive microspheres during TARE and lung shunt fraction assessment has led to inconsistencies in biodistribution in certain cases. This study employed biodegradable hyaluronic acid (HA) as the backbone and modified with bisphosphonate and methacrylic acid to prepare biodegradable gel microspheres (HAMS) using the water-in-oil emulsification and photo-crosslinking for labeling the diagnostic radionuclide of 99mTc and therapeutic radionuclide of 90Y. Both 99mTc radiolabeled HAMS (99mTc-HAMS) and radiolabeled 90Y-HAMS (90Y-HAMS) were highly efficient in radiolabeling and exhibited excellent radiostability in vitro and in vivo. 99mTc-HAMS are highly effective in assessing the LSF, while 90Y-HAMS, administered though TARE, are effective in inhibiting the growth of in situ HCC without any side effects. Both 99mTc-HAMS and 90Y-HAMS have promising clinical applications in HCC theranostics.

Silk fibroin-based embolic agent for transhepatic artery embolization with multiple therapeutic potentials

BACKGROUND

The excellent physicochemical and biomedical properties make silk fibroin (SF) suitable for the development of biomedical materials. In this research, the silk fibroin microspheres (SFMS) were customized in two size ranges, and then carried gold nanoparticles or doxorubicin to evaluate the performance of drug loading and releasing. Embolization efficiency was evaluated in rat caudal artery and rabbit auricular artery, and the in vivo distribution of iodinated SFMS (125I/131I-SFMS) after embolization of rat hepatic artery was dynamically recorded by SPECT. Transhepatic arterial radioembolization (TARE) with 131I-SFMS was performed on rat models with liver cancer. The whole procedure of selective internal radiation was recorded with SPECT/CT, and the therapeutic effects were evaluated with 18 F-FDG PET/CT. Lastly, the enzymatic degradation was recorded and followed with the evaluation of particle size on clearance of sub-micron silk fibroin.

RESULTS

SFMS were of smooth surface and regular shape with pervasive pores on the surface and inside the microspheres, and of suitable size range for TAE. Drug-loading functionalized SFMS with chemotherapy or radio-sensitization, and the enhanced therapeutic effects were proved in treating HUH-7 cells as lasting doxorubicin release or more lethal radiation. For artery embolization, SFMS effectively blocked the blood supply; when 131I-SFMS serving as the embolic agent, the good labeling stability and embolization performance guaranteed the favorable therapeutic effects in treating in situ liver tumor. At the 5th day post TARE with 37 MBq/3 mg 131I-SFMS per mice, tumor activity was quickly inhibited to a comparable glucose metabolism level with surrounding normal liver. More importantly, for the fragments of biodegradable SFMS, smaller sized SF (< 800 nm) metabolized in gastrointestinal tract and excreted by the urinary system, while SF (> 800 nm) entered the liver within 72 h for further metabolism.

CONCLUSION

The feasibility of SFMS as degradable TARE agent for liver cancer was primarily proved as providing multiple therapeutic potentials.

Temporary Vascular Occlusion with Retrievable Microvascular Plugs to Protect Normal Liver during Yttrium-90 Radioembolization

This case series describes a technique to protect nondiseased liver parenchyma during transarterial radioembolization (TARE) using microvascular plugs to occlude nontarget vessels temporarily and protect normal liver. This technique, defined as temporary vascular occlusion, was performed in 6 patients, with complete vessel occlusion obtained in 5 of the 6 patients and partial occlusion with flow reduction in 1 of the 6 patients. A statistically significant (P = .001) dose decrease of 5.7 ± 3.1 times was measured using postadministration yttrium-90 positron emission tomography/computed tomography in the protected zone compared with that in the treated zone.

Intrahepatic flow diversion prior to segmental Yttrium-90 radioembolization for challenging tumor vasculature

Background

Hepatic tumors with complex vascular supply or poor relative perfusion are prone to decreased rates of objective response. This is compounded in the setting of Yttrium-90 (Y90) transarterial radioembolization (TARE), which is minimally embolic and flow-dependent, relying on high threshold dose for complete response.

Objective

We describe our experience with intrahepatic flow diversion (FD) prior to TARE of hepatocellular carcinoma (HCC) with challenging vascular supply.

Materials and methods

Between April 2014 and January 2020, 886 cases of coinciding MAA or TARE and bland embolization or temporary occlusion were identified. Intraprocedural embolizations performed for more routine purposes were excluded. FD was performed by bland embolization or temporary occlusion of vessels supplying non-malignant parenchyma in cases where flow was not preferential to target tumor. Lesion characteristics, vascular supply, treatment approach, angiography, and adverse events (AEs) were reviewed. Radiographic response was assessed using mRECIST criteria.

Results

22 cases of FD of focal HCC were identified. Embolics included calibrated microspheres (n ​= ​11), microcoils (n ​= ​4), gelfoam (n ​= ​3), temporary balloon occlusion (n ​= ​2) and temporary deployment of a microvascular plug (n ​= ​1). Post-treatment SPECT-CT dosimetry coverage was concordant with target lesions in all cases. Mean follow-up was 16.7 months (1.4-45 ​mos). Tumor-specific response per mRECIST was 41% complete response, 50% objective response, and 59% disease control rate. No major adverse events or grade 3/4 hepatotoxicity were reported.

Conclusion

Our findings suggest that FD prior to TARE is safe and potentially effective in treating HCC with complex vascular supply or poor tumor perfusion.

Increasing Yttrium-90 Dose Conformality Using Proximal Radioembolization Enabled by Distal Angiosomal Truncation for the Treatment of Hepatic Malignancy

PURPOSE

To evaluate safety and feasibility of improving radiation dose conformality via proximal radioembolization enabled by distal angiosomal truncation where selective administration was not practical.

MATERIALS AND METHODS

Hepatic malignancies treated via angiosomal truncation between January 2017 and March 2019 were retrospectively evaluated. Thirty-three patients (8 women, 25 men; mean age, 62.2 y; range, 36-78 y) underwent 39 treatments. Of treatments, 74.3% (n = 29) were for hepatocellular carcinomas, 10.2% (n = 4) were for cholangiocarcinomas, and 15.4% (n = 6) were for metastatic tumors (1 colorectal adenocarcinoma, 1 pancreatic adenocarcinoma, 3 melanomas, and 1 endometroid carcinoma). Truncation was achieved using temporary embolic devices including a microvascular plug, detachable coil, gelatin slurry, and balloon microcatheter, after which proximal radioembolization was performed. Range of treatment activity was 0.47-5.75 GBq. Technetium-99m macroaggregated albumin and bremsstrahlung single photon emission computed tomography (CT)/CT threshold analysis was conducted to delineate and compare distribution of activity within the treatment angiosome before and after radioembolization.

RESULTS

Dosimetric analysis of 14 patients demonstrated a significant reduction in nontarget liver radiation exposure at 5, 20, and 40% thresholds (P = .002, P = .001, and P = .008, respectively). There were no grade 3 or higher adverse events. There was no significant change in Albumin-Bilirubin grade and Eastern Cooperative Oncology Group Performance Status (P = .09 and P = .74) before and 3 months after the procedure. Truncated arteries were patent on subsequent angiography in 11 cases and on MR angiography or CT angiography in 38 of 39 cases.

CONCLUSIONS

Proximal radioembolization enabled by distal angiosomal truncation is safe and decreases nontarget parenchymal radioembolization dose in cases not amenable to selective administration.

Y90 Radioembolization Dosimetry: Concepts for the Interventional Radiologist

Transarterial radioembolization (TARE) with beta particle emitting microspheres via Yttrium-90 decay has become a fundamental component of the contemporary Interventional Oncology practice. TARE continues to advance as a result of increased utilization, clinical study, technological improvements, and evolving applications. To maximize TARE safety and efficacy, a core understanding of dosimetry is essential. The intent of this overview is to provide the reader with a general survey of radiation physics and biology, device differentiation, patient selection, anatomic assessment, activity administration models, and procedural techniques involved with TARE dosimetry.

Transarterial Radioembolization (TARE) Agents beyond 90Y-Microspheres

Liver malignancies, either primary tumours (mainly hepatocellular carcinoma and cholangiocarcinoma) or secondary hepatic metastases, are a major cause of death, with an increasing incidence. Among them, hepatocellular carcinoma (HCC) presents with a dark prognosis because of underlying liver diseases and an often late diagnosis. A curative surgical treatment can therefore only be proposed in 20 to 30% of the patients. However, new treatment options for intermediate to advanced stages, such as internal radionuclide therapy, seem particularly attractive. Transarterial radioembolization (TARE), which consists in the use of intra-arterial injection of a radiolabelled embolising agent, has led to very promising results. TARE with 90Y-loaded microspheres is now becoming an established procedure to treat liver tumours, with two commercially available products (namely, SIR-Sphere® and TheraSphere®). However, this technology remains expensive and is thus not available everywhere. The aim of this review is to describe TARE alternative technologies currently developed and investigated in clinical trials, with special emphasis on HCC.

Radioembolisation of hepatocellular carcinoma: a primer

Transarterial radioembolisation (TARE) has gained increasing acceptance as an additional/alternative locoregional treatment option for hepatocellular carcinoma, and colorectal hepatic metastases that present beyond potentially curative options. This is a catheter-based transarterial selective internal brachytherapy that involves injection of radioactive microspheres (usually Y-90) that are delivered selectively to the liver tumours. Owing to the combined radioactive and microembolic effect, the findings at follow-up imaging are significantly different from that seen with other transarterial treatment options. Considering increasing confidence among clinicians, refinement in techniques and increasing number of ongoing trials, TARE is expected to gain further acceptance and become an important tool in the armamentarium for the treatment of liver malignancies. So it is imperative that all radiologists involved in the management of liver malignancies are well versed with TARE to facilitate appropriate discussion at multidisciplinary meetings to direct further management. In this article, we provide a comprehensive review on various aspects of radioembolisation with Y-90 for hepatocellular carcinoma including the patient selection, treatment planning, radiation dosimetry and treatment, side effects, follow-up imaging and future direction.

Polymeric materials for embolic and chemoembolic applications

Percutaneous transcatheter embolization procedures involve the selective occlusion of blood vessels. Occlusive agents, referred to as embolics, vary in material characteristics including chemical composition, mechanical properties, and the ability to concurrently deliver drugs. Commercially available polymeric embolics range from gelatin foam to synthetic polymers such as poly(vinyl alcohol). Current systems under investigation include tunable, bioresorbable microspheres composed of chitosan or poly(ethylene glycol) derivatives, in situ gelling liquid embolics with improved safety profiles, and radiopaque embolics that are trackable in vivo. This article reviews commercially available materials used for embolization as well as polymeric materials that are under investigation.

Transarterial Therapy for Colorectal Liver Metastases

Until recently, hepatic arterial therapies (HAT) had been used for colorectal liver metastases after failure of first-, second-, and third-line chemotherapies. HAT has gained greater acceptance in patients with liver-dominant colorectal metastases after failure of surgery or systemic chemotherapy. The current data demonstrate that HAT is a safe and effective option for preoperative downsizing, optimizing the time to surgery, limiting non-tumor-bearing liver toxicity, and improving overall survival after surgery in patients with colorectal liver-only metastases. The aim of this review is to present the current data for HAT in liver-only and liver-dominant colorectal liver metastases.

Transarterial chemoembolization (TACE) for colorectal liver metastases--current status and critical review

BACKGROUND

Transarterial liver-directed therapies are currently not recommended as a standard treatment for colorectal liver metastases. Transarterial chemoembolization (TACE), however, is increasingly used for patients with liver-dominant colorectal metastases after failure of surgery or systemic chemotherapy. The limited available data potentially reveals TACE as a valuable option for pre- and post-operative downsizing, minimizing time-to-surgery, and prolongation of overall survival after surgery in patients with colorectal liver only metastases.

PURPOSE

In this overview, the current status of TACE for the treatment of liver-dominant colorectal liver metastases is presented. Critical comments on its rationale, technical success, complications, toxicity, and side effects as well as oncologic outcomes are discussed. The role of TACE as a valuable adjunct to surgery is addressed regarding pre- and post-operative downsizing, conversion to resectability as well as improvement of the recurrence rate after potentially curative liver resection. Additionally, the concept of TACE for liver-dominant metastatic disease with a focus on new embolization technologies is outlined.

CONCLUSIONS

There is encouraging data with regard to technical success, safety, and oncologic efficacy of TACE for colorectal liver metastases. The majority of studies are non-randomized single-center series mostly after failure of systemic therapies in the 2nd line and beyond. Emerging techniques including embolization with calibrated microspheres, with or without additional cytotoxic drugs, degradable starch microspheres, and technical innovations, e.g., cone-beam computed tomography (CT) allow a new highly standardized TACE procedure. The real efficacy of TACE for colorectal liver metastases in a neoadjuvant, adjuvant, and palliative setting has now to be evaluated in prospective randomized controlled trials.

A review of 3D image-based dosimetry, technical considerations and emerging perspectives in 90Y microsphere therapy

Yttrium-90 radioembolization (⁹⁰Y-RE) is a well-established therapy for the treatment of hepatocellular carcinoma (HCC) and also of metastatic liver deposits from other malignancies. Nuclear Medicine and Cath Lab diagnostic imaging takes a pivotal role in the success of the treatment, and in order to fully exploit the efficacy of the technique and provide reliable quantitative dosimetry that are related to clinical endpoints in the era of personalized medicine, technical challenges in imaging need to be overcome. In this paper, the extensive literature of current ⁹⁰Y-RE techniques and challenges facing it in terms of quantification and dosimetry are reviewed, with a focus on the current generation of 3D dosimetry techniques. Finally, new emerging techniques are reviewed which seek to overcome these challenges, such as high-resolution imaging, novel surgical procedures and the use of other radiopharmaceuticals for therapy and pre-therapeutic planning.

Temporary arterial embolization of liver parenchyma with degradable starch microspheres (EmboCept®S) in a swine model

BACKGROUND

This study aimed to evaluate the embolic properties, time to reperfusion, and histologic changes in temporary embolization of liver tissue with degradable starch microspheres (DSM) in a swine model.

METHODS

In four adult minipigs, DSMs were injected into the right or left hepatic artery on the lobar level until complete stasis of the blood flow was detectable angiographically. The time required to complete angiographically determined reperfusion was noted. The animals were killed 3 h after complete reperfusion, and samples were taken from the liver. Histologic examinations of the embolized liver parenchyma and untreated tissue were performed.

RESULTS

Hepatic arterial embolization using DSMs was technically successful in all cases, with complete blood flow stasis shown by control angiography. A single vial of DSMs (450 mg/7.5 ml) was sufficient to embolize a whole liver lobe in all cases. Angiography showed complete reconstitution of hepatic arterial perfusion after a mean time to reperfusion of 32 ± 6.1 min (range, 26-39 min). Hematoxylin and eosin staining showed no histologically detectable differences between untreated tissue and parenchyma embolized with DSMs except for mild sinusoidal congestion in one case. Indirect in situ DNA nick end labeling staining (TUNEL) showed only single positive hepatocytes, indicating apoptosis.

CONCLUSION

Temporary embolization of the hepatic artery using DSMs is feasible with complete reperfusion after 30 min in pigs. Even after complete arterial blood flow stasis, no extensive tissue damage to the embolized liver parenchyma was observed at histologic examinations in this short-term study.

Side effects of yttrium-90 radioembolization

Limited therapeutic options are available for hepatic malignancies. Image guided targeted therapies have established their role in management of primary and secondary hepatic malignancies. Radioembolization with yttrium-90 ((90)Y) microspheres is safe and efficacious for treatment of hepatic malignancies. The tumoricidal effect of radioembolization is predominantly due to radioactivity and not ischemia. This article will present a comprehensive review of the side effects that have been associated with radioembolization using (90)Y microspheres. Some of the described side effects are associated with all transarterial procedures. Side effects specific to radioembolization will also be discussed in detail. Methods to decrease the incidence of these potential side effects will also be discussed.