F18-choline PET/CT guided surgery in primary hyperparathyroidism when ultrasound and MIBI SPECT/CT are negative or inconclusive: the APACH1 study

Abstract

PurposeTo evaluate the sensitivity of F18-choline (FCH) PET/CT for parathyroid adenoma detection prior to surgery in patients with primary hyperparathyroidism and negative or inconclusive cervical ultrasound and Tc99m-sestaMIBI SPECT/CT.MethodsWe conducted a prospective bicentric study (NCT02432599). All patients underwent FCH PET/CT. The result was scored positive, inconclusive or negative. The number of uptakes and their sites were recorded. The FCH PET/CT result guided the surgical procedure (minimally invasive parathyroidectomy, bilateral cervical exploration, or other in case of multiple or ectopic foci). FCH PET/CT results were compared to the surgical and pathological findings and the follow-up.ResultsTwenty-five patients were included. Mean calcium and PTH levels prior to surgery were 2.76 ± 0.17 mmol/l and 94.8 ± 37.4 ng/l. Nineteen (76%) FCH PET/CTs were scored positive, 3 (12%) inconclusive and 3 (12%) negative, showing 21 cases of uniglandular disease, including 1 ectopic localization and 1 case of multiglandular (3 foci) disease. Mean lesion size was 13.1 ± 8.6 mm. Twenty-four patients underwent surgery. FCH PET/CT guided surgery in 22 (88%) patients, allowing for 17 minimally invasive parathyroidectomies, 1 bilateral cervical exploration for multifocality and 4 other surgical procedures. Two patients with negative FCH-PET/CT underwent bilateral cervical exploration. When dichotomizing the FCH PET/CT results, thereby classifying the inconclusive FCH PET/CT results as positive, the per lesion and per patient sensitivities were 91.3% (95%CI: 72.0–98.9) and 90.5% (95%CI: 69.6–98.8) and the corresponding positive predictive values were 87.5% (95%CI: 67.6–97.3) and 86.4% (95%CI: 65.1–97.1), respectively.Twenty-one (88%) patients were considered cured after surgery. Their mean calcium level after surgery was 2.36 ± 0.17 mmol/l.ConclusionsPreoperative FCH PET/CT has a high sensitivity and positive predictive value for parathyroid adenoma detection in patients with primary hyperparathyroidism and negative or inconclusive conventional imaging results. Bilateral cervical exploration could be avoided in the majority (75%) of patients.

18F-Fluorocholine PET/CT as a second line nuclear imaging technique before surgery for primary hyperparathyroidism

“…The mean size of positive parathyroid lesions on 18 F-fluorocholine PET/CT was 13.1 mm (maximum transverse diameter on CT); the weight of resected glands is not available. There is no doubt that the results obtained in this series are interesting [13]. However, more detailed consideration of the study raises some questions:…”

“…Patients with a negative sestamibi scan have much higher rates of MGD at surgery than those with a positive scan [14,15]; for example, 32% vs. 13% (P < 0.001) in the series by Dy et al [15]. The finding of only one patient with MGD on choline PET in the series by Quak et al raises the question as to the sensitivity for MGD detection [13]. Unfortunately, iOPTH was not measured and no follow-up was available so calcium levels could not be assessed at 6 months to firmly rule out persistent disease, or beyond 6 months to assess for recurrence.…”

“…The prospective study performed by Quak et a positive predictive value of 87.5% [13]. The mean size of positive parathyroid lesions on 18 F-fluorocholine PET/CT was 13.1 mm (maximum transverse diameter on CT); the weight of resected glands is not available.…”

“…The prospective study reported in this issue of the EJNMMI by Quak et al investigated the sensitivity of 18 F-fluorocholine PET/CT in patients with PHPT and negative or inconclusive neck ultrasonography and sestamibi imaging [13]. This application is interesting as sestamibi negativity presents a dilemma.…”

“…Based on the results of 18 F-fluorocholine PET/CT imaging in the series by Quak et al, 18 of 24 patients were able to receive targeted surgery, which is interesting. On the other hand, surgical success, as assessed by early measurement of calcium levels, pointed to surgical failure in 3 of the 24 patients [13]. The authors warn about the risk associated with considering equivocal Binconclusive^fo-ci as positive.…”