Efficacy of Ultrasound-guided Radiofrequency Ablation of Parathyroid Hyperplasia: Single Session vs. Two-Session for Effect on Hypocalcemia

Abstract

To evaluate safety and efficacy of one- vs. two-session radiofrequency ablation (RFA) of parathyroid hyperplasia for patients with secondary hyperparathyroidism (SHPT) and to compare the outcome of both methods on hypocalcemia. Patients with secondary hyperparathyroidism underwent ultrasound guided RFA of parathyroid hyperplasia. Patients were alternately assigned to either group 1 (n = 28) with RFA of all 4 glands in one session or group 2 (n = 28) with RFA of 2 glands in a first session and other 2 glands in a second session. Serum parathyroid hormone (PTH), calcium, phosphorus and alkaline phosphatase (ALP) values were measured at a series of time points after RFA. RFA parameters, including operation duration and ablation time and hospitalization length and cost, were compared between the two groups. Mean PTH decreased in group 1 from 1865.18 ± 828.93 pg/ml to 145.72 ± 119.27 pg/ml at 1 day after RFA and in group 2 from 2256.64 ± 1021.72 pg/ml to 1388.13 ± 890.15 pg/ml at 1 day after first RFA and to 137.26 ± 107.12 pg/ml at 1 day after second RFA. Group 1's calcium level decreased to 1.79 ± 0.31 mmol/L at day 1 after RFA and group 2 decreased to 1.89 ± 0.26 mmol/L at day 1 after second session RFA (P < 0.05). Multivariate analysis showed that hypocalcemia was related to serum ALP. Patients with ALP ≥ 566 U/L had lower calcium compared to patients with ALP < 566 U/L up to a month after RFA (P < 0.05). Group 1's RFA time and hospitalization were shorter and had lower cost compared with Group 2. US-guided RFA of parathyroid hyperplasia is a safe and effective method for treating secondary hyperparathyroidism. Single-session RFA was more cost-effective and resulted in a shorter hospital stay compared to two sessions. However, patients with two-session RFA had less hypocalcemia, especially those with high ALP.

Figure 1

Ultrasound found 4 hyperplastic parathyroid nodules in a patient with secondary hyperparathyroidism (SHPT) and confirmed by ECT. (a) The middle and lower right parathyroid gland (yellow arrow). (b) The lower right parathyroid gland (black arrow). (c) The upper left parathyroid gland (blue arrow). (d) The lower left parathyroid gland (purple arrow). (e) Emission computed tomography (ECT) coronal image shows that nodule has concentration of radioactivity in the initial phase (20 min) and late phase (120 min) of 99 m Tc-sestamibi sequence.

Figure 2

(a) The radiofrequency ablation (RFA) electrode reached the location on the back of the parathyroid gland. (b) Contrast enhanced ultrasound (CEUS) was used to monitor the radiofrequency ablation (RFA) procedures, a buffering zone (green dotted line) around the hyperplastic parathyroid (red dotted line).

Figure 3

We injected 15 ml 0.9% sterile saline solution to create a buffering zone (green dotted line) around the hyperplastic parathyroid (red dotted line) in order to establish a liquid isolation zone >1 cm in depth between the parathyroid and adjacent structures.

Figure 4

Calcium level of Group 1 and Group 2 patients after RFA.

Figure 5

ROC curve of alkaline phosphatase (ALP) shows area under the curve of 0.965, sensitivity of 95.0% and specificity of 94.6% using alkaline phosphatase (ALP) cutoff point as 566 mmol/L.

Figure 6

Calcium level of ALP ≥ 566 mmol/L patients and ALP < 566 mmol/L patients in Group 1 after RFA.

Figure 7

Calcium level of ALP ≥ 566 mmol/L patients and ALP <566 mmol/L patients in Group 2 after RFA.