Endocrine Abstracts

Background: Focused parathyroidectomy has become the standard procedure for patients with sporadic primary hyperparathyroidism (pHPT) fulfilling the criteria for surgical therapy and requires preoperative localization procedures. Ultrasound imaging (US) and ^99mTc-sestamibi-scintigraphy with/without SPECT/CT (SC) are established first line procedures. ¹⁸F-choline PET/CT (PET) has emerged as a novel sensitive and specific method. However, current reimbursement policy in Switzerland limits its use to patients with negative or equivocal first line imaging. The aim of this study was to compare the accuracy, costs and radiation exposure of SC and PET in patients with negative or equivocal US imaging.

Methods: We retrospectively evaluated all US, SC and PET images performed in patients with sporadic pHPT referred for surgery at our institution between March 2017 and June 2021. US imaging was reported diagnostic, equivocal or negative, SC and PET were reported as positive or negative. Parathyroidectomy was considered successful if normal serum calcium levels were observed six months postoperative.

Results: The study included 239 patients of which all underwent US imaging, 164 (68.6%) received SC and 70 (29.3%) PET imaging. The final diagnostic accuracy of a diagnostic preoperative US (n=66) was high with a sensitivity of 100% and a PPV of 95.5%. In patients with equivocal (n=130) or negative (n=42) US, the accuracy of PET was increased when compared to SC (negative US: sensitivity 38.9% vs 87.5%, PPV 77.8% and 91.3%; equivocal US: sensitivity 70.7% vs 95.0%, PPV 92.1% and 90.5%). The estimated total costs per patient with PET as immediate second line imaging following equivocal US would have been 32% higher compared to a stepwise approach, but comparable in patients with initially negative US. Immediate PET imaging would have reduced radiation exposure by approximately 3.6 mSv (41.8%) and 2.4 mSv (32.4%) in patients with negative and equivocal US results, respectively.

Conclusions: The results confirm the superior accuracy of PET vs SC for the localization of parathyroid adenomas in patients with sporadic pHPT and negative or equivocal US imaging. In patients with negative US immediate PET imaging reduces radiation exposure at comparable costs and should be recommended without previous SC.