#5586 EFFICACY OF ABLATION OF PARATHYROID AUTOGRAFTS FOR RECURRENT HYPERPARATHYROIDISM AFTER TOTAL PARATHYROIDECTOMY AND DELTOID AUTO TRANSPLANTATION
Authors: Andres Julia G , Hang Guanqi , Leong Sum , Too Chow Wei , Wong Jiunn 
Published: June 2023

Abstract

Background and Aims
TPDI is the treatment of choice for patients with severe hyperparathyroidism who have failed medical therapy in our centre. The auto-transplantation of parathyroid tissue in the deltoid reduces the risk of permanent hypoparathyroidism. However, there is a risk of recurrent hyperparathyroidism from the implanted parathyroid tissue. Traditionally, these autografts are removed surgically in the event of recurrent hyperparathyroidism exposing the patients to the risk of permanent hypoparathyroidism. We attempted radiologically guided ablation of the implanted tissue to allow near but not complete ablation of the tissue. We aim to report our experience in using this technique to treat patients with recurrent hyperparathyroidism following TPDI.

Method
This is a single centre retrospective study of 9 patients who are on regular dialysis and underwent ablation of their deltoid parathyroid implants at Singapore General Hospital between May 2020 to July 2022. Baseline demographic data, as well as biochemistry results including intact parathyroid hormone (iPTH), serum calcium, phosphorus and alkaline phosphatase (ALP) levels were retrieved from electronic medical records and analysed. We define successful procedure as achieving 2 out of the following 3 criteria: i. &gt;50% drop in iPTH level at 3 months, ii. correction of hypercalcemia at 3 months, iii. off calcimimetic at 3 months

Results
A total of 9 patients underwent ablation of their parathyroid deltoid implants, of which 8 (89%) had thermal ablation and 1 (11%) had cryoablation. 1 patient required a repeat procedure within 3 month as only 50% of the implanted tissue were targeted instead of the intended 80% and another patient had a repeat procedure &gt;3 month after initial unsuccessful procedure. The median age of patients undergoing this procedure was 60 years (IQR 60, 66) and majority were female (5/9, 55.5%). 8 out of 9 patients were on haemodialysis. 7 out of 9 patients (78%) had a successful procedure based on our definition. 6 patients (67%) had a &gt;50% reduction of iPTH at 3 month, 6 patients (67%) were off calcimimetic at 3 months and out of the 5 patients who were hypercalcemic pre procedure, 4(80%) patients had normalisation of hypercalcemia at 3 months. 3 patients (33%) had iPTH &lt; 2x upper limit of normal with only 1 out of the 3 patient requiring high dose oral calcium replacement at 3 months.
Pre ablation levels of PTH decreased from 191.87 ± 93.52 pmol/L to 99.77 ± 111.007 pmol/L (P = 0.773) 1 day after ablation and 92.450 ± 70.235 pmol/L (P = .0450) at 1 month and 91.25 ± 81.25 (P = .024) pmol/L at 3 months. Serum calcium levels decreased from 2.48 mmol/L ± 0.286 pre ablation to 2.11 mmol/L ± 0.322 1 day post ablation (P = 0.007) and remained 2.28 mmol/L ± 0.403 (P = .122) at 3 months post ablation. Serum ALP levels decreased from 478 ± 292.00 pre ablation to 238 ± 157 at 3 months post ablation.
There were no re-admissions and no immediate post procedure complications in all patients. 4 out of 9 patients (44%) required intravenous calcium replacement post- procedure during the same admission.
Limitations of this study are the relatively short follow-up duration and the small number of patients. 2 out of the 9 patients were lost to follow up at 3 months.

Conclusion
Ablation of deltoid parathyroid autografts may be a safe and effective minimally invasive procedure to manage recurrent hyperparathyroidism and minimising the risk of permanent hypoparathyroidism. However, further studies with larger sample sizes and longer follow up duration would be prudent to confirm our findings