Endocrine Abstracts

Objective

Surgery is the only curative treatment for primary hyperparathyroidism. Minimally invasive parathyroidectomy is superior in terms of cure and complication rates and is less costly than inpatient bilateral cervical exploration. Preoperative localization of parathyroid adenoma by imaging is a requirement for outpatient minimally invasive surgery. One of the most frequently used imaging techniques for parathyroid adenoma localization is Tc99m-sestaMIBI SPECT/CT plus cervical echography. However, one-fourth to one-third of patients have non-localizing disease with usual techniques, needing to undergo bilateral cervical exploration. Some factors associated with negative MIBI-SPECT/CT results are presence of thyroid nodules, lower PTH and calcium levels, parathyroid gland of 12 mm or less and previous cervical surgeries. Recent studies suggest the superiority of F18-choline PET/CT for parathyroid adenoma localization, with a reported sensitivity of 80–90% in patients with negative or inconclusive MIBI SPECT/TC. It also showed a superior accuracy for the detection and correct localization of small adenomas. The aim of this study is to evaluate the efficacy of F18-choline PET/CT in patients with negative or inconclusive MIBI SPECT/TC/echography.

Methods

A retrospective observational study was designed in 15 patients with PHPT, studied between 2018 and 2020, with a negative or inconclusive result in echography + MIBI SPECT/TC and a F18-choline performed afterwards. We analysed the efficacy of this imaging technique and described our patient’s characteristics associated with non-localized adenoma with usual techniques.

Results

15 patients (13 women) were included. Mean age was 63 years old. 4 of them had underwent previous cervical surgeries (2 had previous parathyroidectomy, the other 2 had underwent hemithyroidectomy for thyroid nodules). Mean PTH was 138 pg/dl and mean adjusted calcium was 10.45 mg/dl Mean urine calcium excretion in 24 h and the Ca/Cr index were, respectively, 270 mg/24 h and 0.37 mg/mg. 66% (10/15) had T-score < –2.5. 20% (3/15) had nephrolithiasis. All of them had normal kidney function. 54% of patients had concurrent thyroid nodules. 18-choline PET/CT localized hyperfunctioning parathyroid adenomas in 80% of patients with non-localized adenoma with usual image techniques. Mean adenoma size in PET/TC was 7 mm.

Conclusions

F18-choline PET/CT is a valuable tool in localizing parathiroid adenomas not localized with usual techniques (Tc99m-sestaMIBI and echography), specially for those cases with lower calcium and PTH leves and smaller gland size. This will lead to a greater number of patients who are candidates for minimally invasive parathyroidectomy, resulting in more cured patients and less number of complication rates.