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

The takeaway

A new fluorine-18-labeled somatostatin peptide tracer performed as well as the current gallium-68 standard for imaging neuroendocrine tumors, with potential advantages in availability and longer scan windows.

r = 0.91 Correlation
The new fluorine-18 somatostatin peptide tracer showed excellent agreement with the gallium-68 standard in detecting neuroendocrine tumor lesions across 45 patients

What the researchers found

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).

Why it matters

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.

How the study worked

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.

What this study cannot tell us

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.

How to read the evidence

This is a prospective phase 2 comparative study with a predefined noninferiority design, blinded readers, and histologically confirmed diagnoses. While the sample size is modest, the study design is rigorous and the results are statistically sound.

When this study was published

Published in 2024, this study represents cutting-edge developments in peptide-based cancer imaging and could inform upcoming phase 3 trials and clinical adoption decisions.

The bigger picture

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.

Questions still open

Can the lower liver tumor-to-background ratio of the fluorine-18 tracer be improved through protocol optimization?
Will this tracer perform equivalently in grade 3 neuroendocrine tumors and neuroendocrine carcinomas?
Could the fluorine-18 tracer's wider availability improve early detection rates for neuroendocrine tumors in underserved areas?

Common questions

What is somatostatin receptor imaging used for?

Somatostatin receptor imaging uses peptide-based tracers to find neuroendocrine tumors throughout the body. These tumors express somatostatin receptors on their surface, so peptide tracers that bind to these receptors light up on PET/CT scans, helping doctors locate tumors and decide on treatment.

Why would a fluorine-18 tracer be better than the current gallium-68 version?

Fluorine-18 has a longer half-life (110 vs. 68 minutes), giving doctors more flexible scan scheduling. More importantly, fluorine-18 is produced by cyclotrons available at many hospitals, while gallium-68 requires specialized generators — so the new tracer could make these cancer scans accessible to far more patients.

Read the original research

Somatostatin Receptor Imaging with [18F]FET-βAG-TOCA PET/CT and [68Ga]Ga-DOTA-Peptide PET/CT in Patients with Neuroendocrine Tumors: A Prospective, Phase 2 Comparative Study.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 65(3), 416-22

View on PubMed ↗Publisher’s paper ↗

Citation

Dubash, Suraiya; Barwick, Tara D; Kozlowski, Kasia; Rockall, Andrea G; Khan, Sairah; Khan, Sameer; Yusuf, Siraj; Lamarca, Angela; Valle, Juan W; Hubner, Richard A; McNamara, Mairéad G; Frilling, Andrea; Tan, Tricia; Wernig, Florian; Todd, Jeannie; Meeran, Karim; Pratap, Bhavesh; Azeem, Saleem; Huiban, Michael; Keat, Nicholas; Lozano-Kuehne, Jingky P; Aboagye, Eric O; Sharma, Rohini. (2024). Somatostatin Receptor Imaging with [18F]FET-βAG-TOCA PET/CT and [68Ga]Ga-DOTA-Peptide PET/CT in Patients with Neuroendocrine Tumors: A Prospective, Phase 2 Comparative Study.. Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 65(3), 416-22. https://doi.org/10.2967/jnumed.123.266601