An essential practice summary of the new EANM guidelines for parathyroid imaging

Clinical predictors of negative/equivocal SPECT imaging outcomes in primary hyperparathyroidism: Factors calling for 18F-choline-PET

PURPOSE

For minimally invasive surgery of parathyroid adenomas, exact localization diagnostics are essential. Main imaging modalities used for diagnostics are sonography, SPECT with/without CT (traditional imaging) and 18F-choline-PET. The aim of our study was to identify predictors for inconclusive SPECT imaging and subsequently determine in which cases 18F-choline-PET is needed.

METHODS

Retrospective analysis of 138 patients with histologically confirmed primary hyperparathyroidism (pHPT). After sonography, patients underwent SPECT or SPECT/CT imaging, with subsequent 18F-choline-PET in cases of disconcordant results. Logistic regression analysis was used to identify clinical and laboratory factors predictive for negative SPECT results.

RESULTS

Sensitivity rates for sonography, SPECT, SPECT/CT, and choline-PET were 47 %, 49 %, 71.7 %, and 97 %, respectively. Logistic regression revealed lower PTH levels (p < 0.001), presence of structural thyroid disease (p = 0.018), and negative sonography (p < 0.001) as predictive of negative/equivocal SPECT outcome. An additional traditional imaging CT scan to a SPECT enhanced detection odds, as did greater adenoma weight. Urolithiasis, osteoporosis, and calcium values as measurement of activity and duration of disease showed no significant association with the detection rate. Furthermore, our study demonstrated that 18F-choline-PET exhibited remarkable sensitivity in detecting adenomas among patients with negative/equivocal SPECT results.

CONCLUSION

Our study reveals potential predictive factors for a negative/equivocal SPECT outcome in pHPT. Identifying these factors might allow minimizing futile SPECT examinations and perhaps encourage timely utilization of 18F-choline-PET imaging. Our study reinforces the clinical significance of 18F-choline-PET, especially in complex cases with disconcordant results by conventional parathyroid imaging methods.

Molecular imaging of thyroid and parathyroid diseases

INTRODUCTION

Molecular imaging of thyroid and parathyroid diseases has changed in recent years due to the introduction of new radiopharmaceuticals and new imaging techniques. Accordingly, we provided an clinicians-oriented overview of such techniques and their indications.

AREAS COVERED

A review of the literature was performed in the PubMed, Web of Science, and Scopus without time or language restrictions through the use of one or more fitting search criteria and terms as well as through screening of references in relevant selected papers. Literature up to and including December 2023 was included. Screening of titles/abstracts and removal of duplicates was performed and the full texts of the remaining potentially relevant articles were retrieved and reviewed.

EXPERT OPINION

Thyroid and parathyroid scintigraphy remains integral in patients with thyrotoxicosis, thyroid nodules, differentiated thyroid cancer and, respectively, hyperparathyroidism. In the last years positron-emission tomography with different tracers emerged as a more accurate alternative in evaluating indeterminate thyroid nodules [18F-fluorodeoxyglucose (FDG)], differentiated thyroid cancer [124I-iodide, 18F-tetrafluoroborate, 18F-FDG] and hyperparathyroidism [18F-fluorocholine]. Other PET tracers are useful in evaluating relapsing/advanced forms of medullary thyroid cancer (18F-FDOPA) and selecting patients with advanced follicular and medullary thyroid cancers for theranostic treatments (68Ga/177Ga-somatostatin analogues).

18 F-Fluorocholine PET-CT Outshines Sestamibi Scintigraphy in Detecting Parathyroid Adenomas in the Background of Hashimoto's Thyroiditis

Ultrasonography neck and dual-phase 99m Tc-sestamibi (MIBI) scan are standard imaging techniques for the detection of parathyroid adenomas in primary hyperparathyroidism. However, in presence of coexistent thyroid disease or small size of adenomas, the accuracy of these imaging modalities is low and leads to delayed diagnosis. We here present a report of two patients with primary hyperparathyroidism and with a nondiagnostic MIBI scan, who subsequently underwent successful surgery after positive localization of adenomas on 18 F-fluorocholine positron emission tomography-computed tomography.

[Special features of the diagnostics and treatment of hereditary primary hyperparathyroidism]

Between 2% and 10% of patients with primary hyperparathyroidism (pHPT) are diagnosed with hereditary forms of primary hyperparathyroidism (hpHPT). They are more prevalent in younger patients before the age of 40 years, in patients with persistence or recurrence of pHPT and pHPT patients with multi-glandular disease (MGD). The various forms of hpHPT diseases can be classified into four syndromes, i.e., hpHPT associated with diseases of other organ systems, and four diseases that are confined to the parathyroid glands. Approximately 40% of patients with hpHPT suffer from multiple endocrine neoplasia type 1 (MEN-1) or show germline mutations of the MEN‑1 gene. Currently, germline mutations that lead to a specific diagnosis in patients with hpHPT have currently been described in 13 different genes, which enables a clear diagnosis of the disease; however, a clear genotype-phenotype correlation does not exist, even though the complete loss of a coded protein (e.g. due to frame-shift mutations in the calcium sensing receptor, CASR) often leads to more severe clinical consequences than merely a reduced function of the protein (e.g. due to point mutation). As the various hpHPT diseases require different treatment approaches, which do not correspond to that of sporadic pHPT, a clear definition of the specific form of hpHPT must always be strived for. Therefore, before surgery of a pHPT with clinical, imaging or biochemical suspicion of hpHPT, genetic proof or exclusion of hpHPT is necessary. The differentiated treatment approach for hpHTP can only be defined by taking the clinical and diagnostic results of all the abovenamed findings into account.

Diagnosis and treatment of liver metastases of parathyroid carcinoma

INTRODUCTION

Parathyroid carcinoma (PC) is a very rare endocrine malignancy occurring in less than 1% of all cases of primary hyperparathyroidism (pHPT). The liver is the second most common target organ for distant metastases of PC, but no guidelines are available for the diagnosis and treatment of liver metastases. In this study, we attempted to summarize the characteristics of the diagnosis and treatment of liver metastases based on our patients and other cases reported in the literature.

MATERIALS AND METHODS

The files of all patients diagnosed with PC with liver metastases summarized at our center between 2000 and 2022 were reviewed, and three datasets from Medline, Web of Science, and Embase were systematically searched to identify relevant articles.

RESULTS

Three patients with liver metastases from our center and 11 patients from the literature were included in the study. All patients had pHPT with borderline remission of hypercalcemia after each operation. A total of 71.4% of the patients' liver lesions were found by abdominal CT scans, while 35.7% were found by MRI, PET-CT, and fine-needle aspiration biopsy (FNAB), which were also helpful for diagnosis. Eight of nine patients (88.9%) who underwent surgery, radiofrequency ablation (RFA), or transcatheter arterial embolization (TAE) were alive, and only one postoperative patient died after a follow-up of 60 months.

CONCLUSIONS

PC is a rare malignant tumor prone to recurrence and metastasis, and postoperative reviews should be carried out routinely. Abnormally elevated parathyroid hormone (PTH) and serum calcium can indicate recurrence or metastasis. Enhanced CT and MRI can provide valuable support for the diagnosis of liver metastases, but whether [18F]FDG-PET-CT, [18F]FCH-PET-CT, or [11C]choline-PET-CT can be used as a diagnostic basis requires further study. Resection of liver metastases, segmental hepatectomy, or RFA can significantly improve patients' symptoms.