SAT-546 Endoscopic Ultrasound-Guided Radiofrequency Ablation (EUS-RFA) as an Alternative to Adrenalectomy for the Treatment of Aldosterone-Producing Adenomas (APAs)

Primary Aldosteronism (PA) carries significant cardiometabolic risk, over and above those attributable to hypertension alone. The Endocrine Society guidelines recommend adrenalectomy in those with unilateral disease. However surgery is likely to become unsustainable in public healthcare systems as more patients are diagnosed with PA. Already, surgery may not be feasible in some patients due to co-morbidities, others are reluctant to have the whole adrenal gland removed when excess aldosterone can be localised to small APA(s) in 1 gland.

The FABULAS Study explores if EUS-RFA is a safe alternative to left-sided adrenalectomy (ClinicalTrials.gov ID NCT03405025). This multicentre phase-1 study comprises 3 groups of 10 patients with proven PA and left APAs. Successive groups have an increasing benefit:risk ratio for surgery. The first 4 ablation procedures are assessed by an independent safety committee before progression into the next, overlapping group. The primary outcomes are safety and feasibility of EUS-RFA. Safety is assessed throughout the study, including measures of intra-procedure adrenomedullary activation. Efficacy is evaluated by biochemistry, home / clinic BPs, and quantitative ¹¹C-metomidate PET-CT at baseline and 6 months post-ablation.

RFA is performed using a Starmed catheter, small enough to pass through a 19-gauge needle, through the stomach. Ablation has been performed in 6 patients (median age 63-years). Mean tumour size was 17mm (range 12-36mm). Plasma metanephrine levels remained stable during RFA. 2 adverse events occurred within the first 48hours post-ablation: AF in a patient with known paroxysmal AF, and an episode of pyrexia and raised CRP attributed to tissue infarction. Both events were deemed ‘not unexpected’ by the safety committee. Most patients have benefited clinically post-ablation. This is illustrated by a 65-year-old man with previously uncontrolled hypertension despite 4 antihypertensive medications, including spironolactone. Baseline aldosterone/renin ratio (ARR) was >200 (PA likely if ARR>60). PET CT revealed a 15mm left adrenal nodule with avid metomidate uptake and an SUVmax ratio of 1.92 (SUVmax ratio >1.25 suggestive of unilateral disease). He underwent uneventful EUS-RFA. 6 months post-ablation his ARR has normalised to 26. On repeat PET CT the metomidate avid adenoma is no longer hot, with a drop in both the SUVmax measured over the APA (31 pre-, and 5 post-ablation) and a reduction in the SUVmax ratio to 1.04. Most importantly, his home BP averages 124/83mmHg and he is thrilled to be off all treatment.

Retrospective reports exist of successful percutaneous and retroperitoneal RFA of APAs. FABULAS is the first prospective study, using a minimally invasive, endoscopic route. If proven to be safe and effective EUS-RFA will open the doors for more patients to receive definitive treatment, potentially even those with bilateral disease.