Localization of parathyroid adenomas using 11C-methionine pet after prior inconclusive imaging

Abstract

Purpose: Minimally invasive parathyroidectomy (MIP) is the recommended treatment in primary hyperparathyroidism (pHPT) for which accurate preoperative localization is essential. The current imaging standard consists of cervical ultrasonography (cUS) and MIBI-SPECT/CT. ¹¹C-MET PET/CT has a higher resolution than MIBI-SPECT/CT. The aim of this study was to determine the diagnostic performance of ¹¹C-MET PET/CT after initial inconclusive or negative localization.

Methods: We performed a retrospective single center cohort study of patients with pHPT undergoing parathyroid surgery after prior negative imaging and later localization by means of ¹¹C-MET PET/CT between 2006 and 2014. Preoperative localization by ¹¹C-MET PET/CT was compared with later surgical localization, intraoperative quick PTH (IOPTH), duration of surgery, histopathology, and follow-up data. Also, differences in duration of surgery between the groups with and without correct preoperative localization were analyzed.

Results: In 18/28 included patients a positive ¹¹C-MET-PET/CT result corresponded to the surgical localized adenoma (64%). In 3/28 patients imaging was false positive and no adenoma was found. In 7/28 patients imaging was false negative at the side of the surgically identified adenoma. Sensitivity of ¹¹C-MET PET/CT was 72% (18/25). Duration of surgery of correctly localized patients was significantly shorter compared to falsely negative localized patients (p = 0.045).

Conclusion: In an intention to treat ¹¹C-MET-PET/CT correctly localized the parathyroid adenoma in 18/28 (64%) patients, after previous negative imaging. A preoperatively correct localized adenoma leads to a more focused surgical approach (MIP) potentially reducing duration of surgery and potentially healthcare costs.

Keywords: 11C-methionine positron emission tomography (11C-MET PET); Minimally invasive parathyroidectomy (MIP); Primary hyperparathyroidism (pHPT).

Fig. 1

Patient example of a negative MIBI-SPECT/CT and a positive ¹¹C-MET PET/CT. Planar anterior image of the neck with ^99mTc-pertechnetate (a), early ^99mTc-MIBI (b), and late ^99mTc-MIBI (c). Both planar subtraction image (early ^99mTc-MIBI minus ^99mTc-pertechnetate image (d)) and ^99mTc-MIBI SPECT-CT (E1-SPECT image only and E2 fused SPECT/CT image) do not show a clear focus suspect for adenoma. The ¹¹C-MET PET/CT showed a small lesion located caudally from the left thyroid gland, suspicious for parathyroid adenoma (red arrow F1-PET image only and F2-fused PET/CT image)