New resorbable embolic agent for uterine fibroid embolization is effective

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Resorbable
Nigel Hacking

A new, spherical resorbable gelatine embolic agent, GelBead, has been shown to be “very effective” for uterine fibroid embolization (UFE). Nigel Hacking (Department of Clinical Radiology, University Hospitals Southampton, Southampton, UK) presented this result at the 2018 annual meeting of the Cardiovascular and Interventional Radiological Society of Europe (CIRSE; 22–25 September, Lisbon, Portugal).

This embolic agent is already available in the USA under the name GelBead (Vascular Solutions/ Teleflex; distributed by Medtronic), and is due for commercial release in Europe soon, where it will be called Optisphere.

GelBead is a purified porcine skin derivative (Hacking noted: “Interestingly, gelatine sponge and even trisacryl microspheres come from pigs. Gelatine products have been used for decades”), and has good mechanical strength. Hacking detailed the embolic agent to the CIRSE audience, saying, “This product does degrade, unlike most of the polymer or plastic embolic agents, in around four to nine weeks, and in animal studies it had completely gone at 12 weeks.

“Those of you who have young children will know that plastics are bad, microplastics are worse, and this is one of the first non-plastic or polymer agents we have used. Not to say that the plastics cause any trouble—I do not think they do—but it is interesting that we may be moving towards resorbable agents in the future.”

Hacking and colleagues first conducted a pilot study, before enrolling a larger scale study evaluating GelBead in UFE in comparison with five established and commonly used embolic agents. GelBead compared very favourably to the existing agents. Those also under investigation for comparative purposes were: Gelfoam slurry (Spongostan Special: J&J Medical), trisacryl gelatine microspheres (Embospheres, Merit Medical), Beadblock (Biocompatibles), Embozenes (Celonova), and particulate PVA (Contour, Boston Scientific).

Twenty-five women with symptomatic fibroids participated in the study, and all had a gynaecological assessment prior to treatment. The investigators took an MRI at baseline, and again three months’ postprocedure, to assess uterine size, number and position of fibroids, and size of dominant fibroid. Concerning the decision to have a three-month follow-up period, Hacking explains, “We know that three month MRI predicts beautifully what will happen in the future. You will get good symptomatic improvement. If you can kill all the fibroids, they will not come back. If you only kill some of them, they will come back. So you do not need more than three months.”

Describing the assessment criteria of the study, Hacking said that he and his team did “something that is not all that common in these [types of] trials; we wanted to look at ovarian function, and whether this resorbable agent was more gentle on the ovaries, perhaps. So we looked at the anti-mullerian hormone (AMH) to assess ovarian reserve, and our endpoint was percentage fibroid devascularisation.”

Hacking reported a 95% dominant fibroid complete devascularisation. “We had three groups: 100% [fibroid devascularisation], 90–99%, and less than 90%. We considered less than 90% a failure,” he said. Dominant fibroid devascularisation was below 90% for all the other embolic agents investigated, except for PVA, which had very similar results to GelBead. The other four agents were between 70% and 85%. However, Hacking noted that this study “is not a randomised controlled trial (RCT)”, saying “I respect the RCT data.”

Looking at total fibroid devascularisation data, Hacking comments “If you have got five fibroids or 25 fibroids, to get the 100% [fibroid devascularisation] you have to kill every last bit of every last fibroid, so that is quite a challenge.” When using GelBead, 80% of all fibroids had complete devascularisation. Of this, Hacking said, “GelBead did very well, slightly less well than PVA [85% of fibroids had complete devascularisation in this group], but there was no statistical difference with GelBead any of these other embolic agents investigated, so it is working well. It is reducing the uterus volume, it is reducing the dominant fibroids, which you would expect, and of course the symptoms have improved.”

Moreover, there was no increased permanent uterine artery occlusion, meaning that repeat procedures in cases of future fibroid regrowth are possible. The study investigators found that 75% of patients in the GelBead cohort had bilateral uterine artery patency on MRI at three months. “Our temporary agent, Gelfoam, that we have used for decades, has a bilateral occlusion rate, at least in my hands, of just over a half, a unilateral occlusion rate of 40%, and only 5% with bilateral patency—very strange. If you look at the others though, bilateral patency even with Embospheres is only 55%; remember it is gelatine based. Bead block, Embozenes and PVA are all better [with a bilateral patency result of 94%, 85% and 75%, respectively]. GelBead is pretty good.”

However, Hacking also acknowledges that he changed his technique slightly: “I pushed the GelBead a bit deeper into the uterus, so I think I am cheating slightly compared to the Gelfoam, but those are still quite impressive figures.”

No reduction in ovarian function

Of these results, Hacking commented: “We got good uterine and dominant fibroid reduction [37% and 46%, respectively] and no significant drop in the AMH levels, representing no significant drop in ovarian function.” All of the patients in this study were over 40, so no conclusions can be drawn concerning fertility from this work, and Hacking advised further studies in younger women be conducted. Noting that this was “pure conjecture”, Hacking nevertheless proposed that the idea behind using a completely bioresorbable embolic agent is that “if you do not damage ovarian function, the younger women that we might be able to treat, might not only be able to conceive, but might be able to carry a healthy pregnancy.”

There was a mean reduction in the symptom score as well over the course of the study. At three months’ followup, the average UFS symptom score was 17, compared with 63 at baseline. Additionally, the majority of patients experienced significant improvements in their quality of life, with most of the 25 women involved in the study saying the treatment was “life changing”. However, speaking of the change in quality of life observed in these patients, Hacking emphasised that this particular finding is not new: “We sort of know this already with all the embolic agents.”

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