June 22-25 | Nice, France
June 22-25 | Nice, France
June 22-25 | Nice, France
June 22-25 | Nice, France
June 22-25 | Nice, France
TARE: Procedural and technical aspects
Trans-arterial radioembolisation (TARE) has gained worldwide acceptance as a safe and effective treatment for primary and metastatic unresectable liver cancer [1-3]. Through selective administration of microspheres loaded with beta-emitting isotopes, the goal is to deliver a tumoricidal absorbed dose to liver tumours while sparing healthy liver tissue and limiting systemic toxicity .
However, the success of the procedure is strictly related to multiple clinical and technical factors:
- Patient selection, including liver function, performance status, tumour burden and previous medical history, such as previous transarterial therapies [5-6];
- Dosimetry, to be personalized based on tumour histology, treatment goal and type of microspheres [6-10];
- Precise and complete tumour targeting ;
- Microspheres’ distribution which may vary according to several parameters, such as tumour extension and vascularisation, position and orientation of the microcatheter, injection velocity, number of administered spheres [11-13].
Thus, the preliminary diagnostic work-up becomes essential for planning the best strategy to enhance complete and homogeneous tumour targeting while limiting non-target embolisation.
The diagnostic work-up can be summarized in few essential steps:
1) Identification of all tumour arterial feeders, with evaluation of their haemodynamics
In the case of multiple feeders from different branches, it is important to assess if all feeders are able to receive a proper quantity of spheres based on their vascularisation territory. Frequently, there may be major and minor tumour feeders, and the latter may require coil embolisation at a proximal level to enable flow redistribution, reducing the number of injection points (Figure 1) [14,15].
Flow redistribution requires an in-depth knowledge of the possible intra- and extra-hepatic arterial connections, and it should be performed only when strictly needed, since it may be tricky and unpredictable, varying upon vascular anatomy, tumour type and location . The success of flow redistribution has been reported to be lower when parasitized arteries are embolised proximally , as well as in centrally located tumours when unilobar treatment is planned . Moreover, lower success rates have been reported in hypervascular bulky lesions, such as neuroendocrine metastases, which can result in unpredictable collaterals .
2) Identification of any extrahepatic vessel originating from the target area
Non-target embolisation may expose the patient to severe complications due to irradiation of nearby organs, such as the stomach, jejunum, gallbladder, and so on. The diagnostic work-up always requires at least the identification of the origin of the left and right gastric arteries and the cystic artery. When needed, these arteries require embolisation to avoid possible complications.
Whether the cystic artery can be overlooked is still a matter of debate. Our local policy is to avoid including the cystic artery in the treatment territory, placing the microcatheter distal to its origin, and even splitting doses into different injection points, if needed (Figure 2). This is particularly true when dealing with relatively hypovascular lesions, such as metastases, in which we are not able to rely on the preferential flow into the tumour feeding vessels. Permanent embolisation of the cystic artery is usually avoided, since ischaemic cholecystitis may occur.
To identify possible non-target embolisation areas, the use of cone-beam CT is highly recommended. Also, when identifying suspicious arteries during diagnostic angiography, even if the entire branch is not fully recognized, its selective catheterisation should be performed to rule out possible connections with non-target areas (Figure 3).
3) Optimisation of catheter position and tip orientation
Previous studies have clearly demonstrated how spheres’ distribution is strongly influenced by the catheter’s position and orientation [11-13]. For instance, when positioning the catheter close to an arterial bifurcation, a preferential flow into one of the two branches is frequently observed, which may be determined by the distal vessels’ size and their area of distribution as well as by the morphology and the orientation of the catheter’s tip. The tip’s orientation is influenced by the anatomy of the more proximal vessels, and the type and position of the supporting 5 Fr catheter. The challenge for the operator is to select the most proper position of the catheters to obtain a homogeneous flow distribution in the entire target volume. To do so, changes in position of the supporting catheter as well as of the microcatheter should be attempted until the optimal flow distribution is obtained.
4) Reproduction of the injection velocity
During the preliminary work-up, operators need to be aware of the striking differences in injection velocity when using power injections compared to manual injections. Considering that the treatment will be performed by slow manual injections, the final evaluation of flow distribution and the administration of the Technetium-99m-labelled Albumin MacroAggregates should always be performed by manual injections, trying to reproduce the injection velocity that will be used during the treatment dose administration.
University Hospital of Pisa, Pisa/IT
Dr. Irene Bargellini is interventional radiologist at the University Hospital of Pisa in Pisa, Italy. She received her medical degree from the University of Pisa in 1999, completed her radiology residency in Pisa in 2003 and received a master degree in Interventional Radiology in 2017.
The main focus of her clinical and scientific work is on oncologic imaging and interventional oncology, with particular reference to liver imaging and liver tumors’ loco-regional and systemic therapies. Dr. Bargellini is active member of the Italian Society of Radiology (SIRM), European Society of Radiology (ESR), European Society of Gastrointestinal and Abdominal Radiology (ESGAR), Cardiovascular and Interventional Radiology Society in Europe (CIRSE) and the International Liver Cancer Association (ILCA).
She serves as reviewer of several national and international journals; she has been vice-director of Giornale Italiano di Radiologia Medica and member of the Editorial Board of European Radiology and Cardiovascular and Interventional Radiology. She has authored and co-authored more than 90 articles in peer-review journals, is co-author of several book chapters, and has given over 260 invited lectures at national and international meetings.
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