New Fluorine-18 Peptide Tracer Matches Standard Gallium-68 Scans for Detecting Neuroendocrine Tumors

In 45 patients with grade 1-2 neuroendocrine tumors, [18F]FET-βAG-TOCA PET/CT was noninferior to [68Ga]Ga-DOTA-peptide PET/CT. Both tracers detected 285 lesions with excellent SUVmax correlation (r = 0.91). The fluorine-18 tracer detected 13 additional tumor deposits in 8 patients that the gallium-68 scan missed, while the gallium-68 tracer found 7 additional lesions in 5 patients. The only significant difference was in liver metastases, where the gallium-68 tracer showed better tumor-to-background ratios (3.5 vs. 2.5, p<0.05).

This was a prospective, phase 2 noninferiority study. Forty-five patients with histologically confirmed grade 1-2 neuroendocrine tumors underwent PET/CT imaging with both tracers within a 6-month window (median 77 days apart). Whole-body scans were performed 50 minutes after injection of 165 MBq of the fluorine-18 tracer. Two unblinded readers evaluated tracer uptake, and three experienced readers performed a randomized, blinded reading at the regional level.

Gallium-68-labeled peptide scans are the gold standard for neuroendocrine tumor imaging but are limited by gallium-68's short half-life (68 minutes) and the need for specialized generators. Fluorine-18 has a longer half-life (110 minutes) and is produced by widely available cyclotrons, meaning this new peptide tracer could dramatically expand access to somatostatin receptor imaging worldwide.

Somatostatin receptor imaging is essential for managing neuroendocrine tumors — it guides treatment decisions including whether patients are candidates for peptide receptor radionuclide therapy. A fluorine-18 alternative that matches gallium-68 performance could democratize access to this critical imaging modality, particularly in centers without gallium-68 generators.

The sample size of 45 patients is relatively small for a noninferiority study. The median 77-day gap between scans means disease could have progressed between imaging sessions. The fluorine-18 tracer showed lower tumor-to-background ratios in the liver, which could limit its utility for detecting liver metastases specifically. Readers were unblinded for the primary analysis.