GAE’s growing evidence base broadens scope for future NICE recommendation

Mark Little presenting at BSIR 2022

Mark Little (Royal Berkshire Hospital, Reading, UK) brought delegates up to speed on genicular artery embolization (GAE) for knee osteoarthritis over two sessions at the recent British Society of Interventional Radiology (BSIR) annual scientific meeting (2–4 November, Glasgow, UK). Little led audience members through the existing body of evidence for GAE’s safety and efficacy, before outlining the roadmap for growing this further in order to gain UK National Institute of Health and Care Excellence (NICE) recommendation.

“We set up the first European study [GENESIS] back in 2017 and the interim analysis was published in CVIR [CardioVascular and Interventional Radiology] last year.” Little began his presentation by offering the BSIR audience background to his research. The participants in the study, he explained, were “patients with mild-to-moderate knee osteoarthritis [OA]”, numbering 38, and who “had to have had at least an attempt at conservative treatment in the six months preceding referral.”

Regarding the method and materials used, Little shared that for GENESIS, he used 100–300-micron Embosphere particles, and “skin-to-skin”, the embolization procedure took “about an hour”.

For both GENESIS and the now-enrolling GENESIS II studies, Little stated the primary outcome as being knee pain and function, assessed according to the Knee Injury and Osteoarthritis Outcome Score (KOOS). The measure of technical success, the presenter elaborated, was carrying out the embolization, which, according to the GENESIS interim analysis was 84%.

Posing the rhetorical question “Why was it not 100%?”, Little gave by way of an answer that they did not embolize six patients. The reasons in each case varied among a “risk of non-target embolization to the skin, anastomotic communication between the genicular and popliteal arteries posing an unacceptable risk of non-target embolization, and a lack of hyperaemia”.

Interim results show “initial improvement sustained to follow-up”, Little declared, before alluding to the fact that, for the one-year data, due for publication in 2023, “the trends are the same”.

Little then addressed the NICE appraisal for GAE that he undertook 18 months ago. NICE recommend research preferably in the form of randomised controlled trials against sham or current best practice. Patient-reported outcome data will also be key, Little reported.

Brain scans and a neuropsychometric questionnaire were also included in the GENESIS trial to evaluate the impact of chronic pain on procedure outcomes. The finding, Little relayed, was that “there is a strong signal between patient catastrophising and poor outcomes” in terms of pain.

Rounding off his coverage of GENESIS, Little concluded that the trial demonstrated that GAE for mild-to-moderate knee OA is “safe with potential efficacy” and has “good scientific rationale”. To prove efficacy and heed NICE’s request for more data, there is GENESIS II, to which the presenter then turned.

This trial began two weeks ago, and is using the same KOOS primary endpoint, with a placebo comparison, the presenter outlined. Patient-reported outcome data will constitute a secondary endpoint, Little added. GENESIS involved a patient questionnaire, from which the results showed that “75% [of participants] would be more than happy to have [the procedure] again”.

Session chair Rob Morgan (St George’s Hospital, London, UK) asked Little whether anyone in the field had gathered data over more than a year—“there are Japanese data to four years,” the presenter replied, following up by affirming that “the effects [are] maintained”.

In the second session of GAE coverage, Little spoke to deepened understanding of knee OA anatomy that has come in the last decade, citing discoveries about vessel formation as “pivotal”.

Pre-empting the question of where GAE fits into the treatment strategy, Little asserted that the majority of knee OA patients are treated by their general practitioner but that many of those will fail conservative therapy, including injections and physiotherapy. Moreover, the presenter went on, “there is a treatment gap between those [whose conservative treatment has] failed and those who are eligible for joint replacement surgery—orthopaedic surgeons do not like to operate on young patients, [for example].”

The current ideal patient, Little communicated, is one with mild-to-moderate knee OA, as these are the individuals in whom the procedure has been trialled to date. There is good data concordance despite slight differences in technique and embolic agent across various centres—“patients get better and then there is a plateau”.

Conrad von Stempel (University College London Hospitals, London, UK) put the question to Little, following his presentation, of how to convince orthopaedic colleagues to refer patients for GAE. According to Little, “these are difficult to treat patients as they will have failed conservative treatments but are not surgical candidates”. Orthopaedic colleagues “are delighted” to have another potential treatment option in the form of GAE. “It is a completely different mindset to traditional turf wars,” Little emphasised.


  1. I’m not in this loop, but I’m certainly curious. What’s the mechanism of pain relief supposed to be? Killing pain sensitive nerve fibers?


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