medwireNews: F18-choline positron emission tomography (FCH PET)/computed tomography (CT) scans may be a better alternative to Tc99m-sestaMIBI (MIBI) single-photon emission (SPE)CT/CT for the surgical management of patients with primary hyperparathyroidism (PHPT), suggest APACH2 trial findings.
FCH PET/CT, a 3-dimensional nuclear medicine technique for localization of parathyroid adenoma, led to more patients being able to undergo minimally invasive parathyroidectomy and achieve normocalcemia than the standard MIBI SPECT/CT, say the researchers. This was due to its superior sensitivity for detecting parathyroid adenomas, which was 82%, compared with 63% for MIBI SPECT/CT.
“Currently, FCH PET/CT is not the first-line imaging technique in the preoperative workup of patients with PHPT,” explain Elske Quak (Centre Françoise Baclesse, Caen, France) and colleagues in JAMA Otolaryngology–Head & Neck Surgery. The reason for this, they add, is because FCH has no market authorization for imaging the parathyroid and FCH PET/CT is more expensive and not as available as MIBI SPECT/CT.
FCH PET/CT has advantages over MIBI SPECT/CT imaging, the authors comment, such as more rapid biokinetics and superior spatial resolution meaning small adenomas can be detected, as well as less exposure to ionizing radiation. However, more investigation into the “downstream clinical impact” of these differences is needed, they point out.
To this end, the researchers carried out the phase 3 trial, which involved 42 women and 15 men with PHPT from four hospitals across France who were eligible for surgery. They had a mean age of 62.8 years.
The participants were randomly assigned to undergo first-line FCH PET/CT (n=29) or MIBI SPECT/CT (n=28) up to 12 weeks before surgery.
FCH PET/CT of the neck and upper chest was conducted 60 minutes after intravenous administration of 1.5 MBq/Kg of the FCH radiotracer and MIBI SPECT/CT was carried out according to the dual-phase protocol.
Overall, 85% of the 27 patients who received first-line FCH PET/CT and were available at follow-up achieved true-positive successful minimally invasive parathyroidectomy and normal serum calcium levels of 10.2 mg/dL (2.55 mmol/L) or less at 1 month after surgery. This compared with 56% of the 25 available peers who instead received MIBI SPECT/CT, giving a significant difference of 29 percentage points.
The researchers note that first-line FCH PET/CT lessened the need for second-line imaging, being positive in 24 patients, whereas first-line MIBI SPECT/CT was positive in only 18 patients. Patients who had a negative result then underwent second-line imaging with the alternative technique.
Quak and team acknowledge that “it would have indeed been preferable and more robust to consider a study design without second-line imaging,” but they say that it “did not seem ethical for treatment of patients.”
Follow-up at 6 months was available for 43 patients and all those who achieved normocalcemia at 1 months still had it at this point, with mean levels of 9.28 mg/dL (2.36 mmol/L).
There were four adverse events – two related to surgery and two to general anesthesia – but none were associated with imaging.
The investigators believe first-line FCH PET/CT to be “superior and safe for preoperative [parathyroid adenoma] localization,” compared with MIBI SPECT/CT.
“We expect these findings to contribute to the marketing authorization of this existing radiopharmaceutical for a new clinical indication.”
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JAMA Otolaryngol Head Neck Surg 2024; doi:10.1001/jamaoto.2024.1421
