Prospective, primarily direct comparison of 11C-methionine PET versus
11C-choline PET, and secondary 4D-CT, to explore what PET tracer to use
and in which order to use the functional versus the anatomical imaging
technique in the setting of primary hyperparathyroidism

Surgery is the recommended and only curative treatment in patients with pHPT,
preferably by means of a minimally invasive parathyroidectomy (MIP). During
MIP, surgeons remove the parathyroid adenoma (PTA) via a unilateral approach
with a minimal invasive incision (1-2 cm). In 80-90% only one PTA is present,
making focused MIP usually successful.
In order to perform a MIP, accurate preoperative imaging is essential.
Worldwide, the current primary preoperative localization-imaging-standard
consists of cervical ultrasonography combined with MIBI-SPECT. When these
techniques are combined a sensitivity of 80-95% can be achieved. However, this
still means that surgeons will have to explore bilaterally in 5-20% of the
cases. 11C-methionine positron emission tomography/CT (11C-MET PET/CT) and
11C-choline PET/CT are nuclear imaging techniques that can be used as a next
step for imaging after prior negative localization. Also, a relatively new
preoperative imaging modality was introduced in 2006 namely four-dimensional
computerized tomography (4D-CT). If these scans do detect a parathyroid
adenoma, surgeons can perform a minimal invasive parathyroidectomy. This
minimal invasive approach has less complications, suchs as infections,
bleedings or nerve damage.
Within the nuclear medicine department, it remains unclear which PET scan
(using 11C-methionine or 11C-choline as a tracer) should be performed after a
negative MIBI-SPECT/CT and/or cUS. In this area more research is warranted, to
explore what and in which order to use the imaging techniques in the setting of
pHPT, in order to perform a focused MIP.

Prospective, primarily direct comparison of 11C-methionine PET versus
11C-choline PET, and secondary 4D-CT, to explore what PET tracer to use and in
which order to use the functional versus the anatomical imaging technique in
the setting of primary hyperparathyroidism

This is a single-center, prospective, blinded cohort study designed to compare
primarily the sensitivity and PPV of 11C-MET PET/CT with 11C-choline PET/CT and
secondary 4D-CT in operable patients with biochemically proven pHPT and prior
negative, inconclusive or discordant parathyroid imaging with an indication for
surgery.

Patients will follow the standard clinical work-up to undergo
parathyroidectomy, including lab parameters, 11C-MET PET/CT, and if necessary
4D-CT. Patients participating in this study, after having given informed
consent, will undergo additional imaging to the standard clinical care; namely
11C-choline PET/CT and if not already performed 4D-CT.

Not applicable

Imaging is very important in patients with primairy hyperparathyroidism (pHPT)
in order to detect enlarged parathyroid glands with the aim of performing a
minimal invasive parathyroidectomy (MIP). In this study we want to evaluate and
compare 11C-methionine PET/CT, 11C-choline-PET/CT and 4D-CT to each other, in
patients with pHPT and prior negative, inconclusive or discordant imaging, to
explore what functional tracer is best and in which order to use the functional
and anatomical imaging. Results of this study will provide valuable information
about the performance of the imaging techniques in patients with pHPT and in
which order to use them. For some patients with pHPT and prior
negative/inconclusive/discordant imaging, the 11C-methionine PET/CT (and 4D-CT)
is negative. Normally these patients would then be scheduled for a bilateral
neck exploration. Because of this study, it is foreseen that the
11C-choline-PET/CT (or 4D-CT) will identify the PTA and these patients can then
still be scheduled for a MIP. So, the benefits may be a less invasive and
shorter procedure, resulting in less time under anesthesia and less time spent
in the operation room. However, in some of the patients it is also possible
that the extra imaging techniques are unnecessary (because 11C-MET PET/CT
already identified the PTA, or all the techniques come up negative). For these
patients the benefits of this study do not directly apply. Nevertheless, their
participation helps to get more insight into the most sensitive PET tracer for
the identification of PTA and the order in which the 11C-methionine PET/CT,
11C-choline-PET/CT and 4D-CT should be applied.

Since patients undergo an extra PET/CT and in some cases a 4D-CT scan, it will
cause additional radiation burden to the patient. 11C-choline-PET/CT implements
a radiation burden of about 2.3 mSv . A 4D-CT results in a radiation burden of
2.5 mSv. This totals to an extra 2.3 mSv (11C-choline PET only) or 4.8 mSv
(11C-choline PET + 4D-CT) for patients participating in this study. Together
the risk category of this study falls in category IIb. Also, patients may be
allergic for the iodinated contrast fluid used in 4D-CT, resulting in a worst
case scenario in shock. While serious allergic to contrast fluids are (very)
rare, radiology departments are well-equipped to deal with them.

Whenever possible, for patient convenience, the 11C-choline PET/CT is
preferably planned on the same day as the 4D-CT. It is not possible to plan the
11C-choline PET/CT on the same day as the 11C-methionine PET/CT. If the
11C-choline PET/CT cannot be planned on the same day as the 4D-CT, for this
study, patients will pay maximum two extra visits to the hospital for the
11C-choline-PET/CT and in some cases the 4D-CT. Thereafter, patients will
receive the parathyroidectomy as planned.
In conclusion, the risk associated with the extra 11C-choline-PET/CT and 4D-CT
seems minor and although some of the patients may not directly benefit from
this study, results of this study will be valuable for our understanding of the
identification of PTA and the order in which the imaging techniques have to be
used to identify them.