Endocrine Abstracts

In primary hyperparathyroidism (pHPT) an exact localization of the pathological parathyroid gland(s) is essential before minimally invasive parathyroidectomy. We have previously shown in a small group of pHPT patients, that ¹¹C-methionine-PET/CT provides additional information if ¹²³I/^99m Tc-sestamibi (MIBI) scan remains negative. The aim of the present study was to evaluate the clinical value of ¹¹C-Met-PET/CT in a larger pHPT patient cohort.

Methods: Totally 89 patients with pHPT (66 females, 23 males, age 18-81 years) and negative or inconclusive localisation findings with ¹²³I/^99mTc- MIBI-SPECT/CT (78,7%) or ^99mTc-MIBI-SPECT/CT (21.3%) were studied with ¹¹C-Met-PET/CT. Most of the patients (87.6%) were surgical treatment naive and the rest of them (12.4%) were previously operated 1–2 times.

Results: ¹¹C-Met-PET/CT revealed the pathologic parathyroid gland in 48 (60.8%) of the 79 surgically treated patients. Totally 26 patients (32.9%) had a negative ¹¹C-Met-PET/CT finding and 16 of them had further explorative surgery, whereas 10 of these Met-PET negative patients were not operated, but treated conservatively instead. In five cases (6.3%) Met-PET detected a false-positive finding, i.e. the pathological parathyroid gland was found in another location. On a per-lesion level PET results were 48 true positive (60.8%) and 21 false negative (26.6%). The lesion-based sensitivity was 75.4% (positive predictive value 94.6%) and specificity 40.0% (negative predictive value 10.5%). The diagnostic accuracy of ¹¹C-Met-PET/CT in this study was 73%. Based on the histological examinations 67 adenomas (84.8%) and six hyperplastic (7.6%) parathyroid glands were found. In five cases the finding was normal parathyroid tissue or unspecified. Ten patients (12.7%) had more than one pathological parathyroid glands. There were no parathyroid carcinomas detected in this study. Totally 79 patients had parathyroid surgery and 55 (69.6%) of them were biochemically cured, but in 16 patients (20.3%) pHPT persisted and in eight patients (10.1%) the postoperative status remained unknown.

Conclusion: ¹¹C-methionine-PET/CT offers an additional noninvasive imaging method to localize hyperfunctiong parathyroid glands in a situation when conventional imaging methods ^99mTc or ¹²³I/^99mTc-sestamibi SPECT/CT fail or are equivocal.