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

Abstract

Purpose: To 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.

Methods: We 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.

Results: Twenty-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.

Conclusions: Preoperative 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.

Keywords: F18-choline; MIBI SPECT/CT; Minimally invasive surgery; PET/CT; Parathyroid adenoma; Primary hyperparathyroidism.

Conflict of interest statement

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study (Ref. 2014–41, Comité de protection des personnes Nord-Ouest III).

Figures

Fig. 1

Flow chart of patients through the study. MIP minimally invasive parathyroidectomy, BCE bilateral cervical exploration, UCE unilateral cervical exploration, AE adverse event, PTA parathyroid adenoma, PHPT primary hyperparathyroidism

Fig. 2

Semi-quantitative analyses of the (a) PTA-to-muscle ratio (b) PTA-to-thyroid ratio and (c) noise level in the muscle background for the list-mode PET acquisitions reconstructed with an increment of 2 min

Fig. 3

FCH PET/CT images of a 66-y-old male patient with PHPT and negative cervical ultrasound and MIBI SPECT/CT. (a) FCH PET maximum-intensity-projection, (b) FCH PET/CT fusion transverse slice, and (c) low-dose CT transverse slice, showing increased FCH uptake in a flat PTA in the left superior position (red arrow). Resection of a flat left superior PTA was performed by minimally invasive parathyroidectomy, leading to cure

Fig. 4

MIBI SPECT/CT and FCH PET/CT images of a 68-y-old female patient with PHPT, an inconclusive cervical ultrasound report (dubious right inferior focus only visible on one plane) and a negative MIBI SPECT/CT. (a) MIBI SPECT maximum-intensity-projection, (c) MIBI SPECT/CT transverse slice, (b) FCH PET maximum-intensity-projection, and (d) FCH PET/CT transverse slice. The MIBI and FCH MIP images (a, b) did not show clear focal uptake in the lower neck. However, the FCH PET/CT transverse slice (d) showed increased FCH uptake in a small ectopic deep-laying left-sided PTA in the upper mediastinum, which was negative on MIBI SPECT/CT (c) (red arrows). Successful ectopic parathyroidectomy was performed, leading to cure