Studies evaluate the usability of 18F-choline (FCH) in the diagnosis of hyperparathyroidism

Primary hyperparathyroidism (pHPT) is a common endocrine disorder that is mainly treated surgically. However, in order to allow for a minimal invasive parathyroidectomy (MIP) procedure, it is fundamental to obtain adequate pre-operative imaging. Because conventional imaging is often inconclusive, a new methodology applying (18)F-fluorocholine (FCH) PET-CT has been recently tested by Dr. W. P. Kluijfhout and colleagues in a series of patients as a possibly superior imaging modality for the localization of pathological parathyroid glands, and hence for diagnosis of pHPT.
The uptake of the radioisotope 18F-fluorocholine is increased in pathological parathyroid glands. Thus, FCH PET-CT takes advantage of the combined ability of PET-CT and (18)F-fluorocholine to help clinicians locate the pathological parathyroid glands where conventional modalities, such as SPECT-CT (single photon-emission computed tomography-computed tomography), cannot. This way, surgeons are enabled to accomplish targeted minimal invasive surgery, which may prevent a more extensive operatory exploration as well as its associated risks, and decrease the patient’s need for medications with side effects [1]. Despite the scarce literature available on this methodology, preliminary results are promising, as shown by the following examples.
In one study [2], a 57 year-old man presenting with complaints of fatigue had biochemical primary hyperparathyroidism detected by laboratory tests. Whereas conventional imaging consisting of neck ultrasound and 99Tcm-sestamibi SPECT-CT could not localize the pathological gland, subsequent FCH PET-CT clearly identified an adenoma dorsally of the left thyroid lobe, which was removed at that exact location via MIP. The diagnosis of adenoma was confirmed by histological examination.
This first report of a case with negative ultrasound and sestamibi SPECT-CT imaging, but FCH PET-CT ultimately prompting successful minimal invasive surgery, was followed by the report of 63 consecutive patients, in a single institution, with diagnosis of non-familial pHPT receiving the same treatment [3]. This study as well had the aim of assessing the diagnostic value of ultrasound and SPECT-CT as well as FCH PET-CT for preoperative localization of hyper-functioning parathyroids. Surgical findings were used to establish the sensitivity and the positive predictive value (PPV) of the different imaging modalities.
Of the evaluated patients, 42 (66.7%) underwent MIP. PPV (93.0%) and sensitivity (80.3%) of SPECT-CT were significantly higher than for ultrasound (US) (78.3% and 63.2%, respectively). Adding US to SPECT-CT for initial pre-operative localization did not significantly increase sensitivity, but indeed significantly decreased PPV. The effectiveness of US was significantly higher when performed after SPECT-CT. FCH PET-CT was able to localize the hyperfunctioning parathyroid gland in four of five cases with discordant conventional imaging, thus enabling MIP.
These results suggest SPECT-CT as the imaging modality of choice for initial pre-operative localization of hyperfunctioning parathyroid glands in patients with biochemical pHPT.  Subsequently, ultrasound should be performed for confirmation of positive SPECT-CT findings and for pre-operative marking, allowing MIP. In case of negative or conflicting imaging, additional FCH PET-CT should be considered.
As shown above, the preliminary results for the tested diagnostic application of FCH PET-CT are promising. Since any hospital having PET-CT equipment may perform the scan, and (18)F-fluorocholine is widely available, the FCH PET-CT method is expected to become more frequently employed in hyperparathyroidism, and clinicians should consider it as a second line modality for optimal patient care. 
 
References:
[1] Kluijfhout WP, Vriens MR, Borel Rinkes IH, Valk GD, de Klerk JM, de Keizer B. [18F-Fluorocholine PET-CT for localization of parathyroid adenomas]. Ned Tijdschr Geneeskd. 2015;159:A 8840 [Article in Dutch]. PMID: 26043254.


[2] Kluijfhout WP, Vriens MR, Valk GD, Barth RE, Borel Rinkes IH, de Keizer B.(18)F-Fluorocholine PET-CT enables minimal invasive parathyroidectomy in patients with negative sestamibi SPECT-CT and ultrasound: A case report. Int J Surg Case Rep. 2015;13:73-5. PMID: 26117451.
[3] Kluijfhout WP, Vorselaars WM, Vriens MR, Borel Rinkes IH, Valk GD, de Keizer B. Enabling minimal invasive parathyroidectomy for patients with primary hyperparathyroidism using 99Tcm-sestamibi SPECT-CT, ultrasound and first results of (18)F-fluorocholine PET-CT. Eur J Radiol. 2015 Sep;84(9):1745-51. PMID: 26047823.