Breakthrough in Nuclear Medicine and Molecular Imaging: European Study Reveals Application of One-Day Dual-Tracer PET/CT Imaging in Neuroendocrine Tumors

In the field of nuclear medicine, neuroendocrine neoplasms (NENs), known for their heterogeneity and complexity, have consistently been a focal point of research. A team from Tübingen, Germany, has published an innovative study in the European Journal of Nuclear Medicine and Molecular Imaging. The study explores the impact of one-day dual-tracer positron emission tomography/computed tomography (PET/CT) imaging on the clinical management of NEN patients.

Background

Neuroendocrine neoplasms are a heterogeneous group of tumors originating from different anatomical sites, with varying levels of differentiation. They are categorized into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). For effective treatment stratification, current clinical practice often relies on somatostatin receptor (SSTR)-PET imaging. However, certain high-proliferating or poorly differentiated NENs exhibit high glucose metabolism and low SSTR expression, making SSTR-PET imaging insufficient to fully assess disease burden. As a solution, researchers have proposed a novel strategy combining [18F]FDG (fluorodeoxyglucose) with radiolabeled somatostatin analogs (SSAs) for dual-tracer imaging.

Study Context

The study team, comprising Eduardo Calderón, Lena S. Kiefer, Fabian P. Schmidt, and others, is primarily associated with the Department of Nuclear Medicine and Clinical Molecular Imaging at the University Hospital Tübingen and related departments. Published in 2025, this study represents the latest contribution to the field of neuroendocrine tumor imaging diagnostics.

Study Design and Methods

The core of this study is the feasibility assessment of a one-day dual-tracer imaging protocol. The protocol includes:

1. Low-Activity [18F]FDG PET Scan: The study involved 20 NEN patients, who first underwent an [18F]FDG PET scan at a low administered activity of 0.5 MBq/kg. A whole-body scan covering areas from the head to mid-thighs was conducted 60 minutes post-injection.
2. Standard-Activity [18F]Sifalin-Tate PET Scan: Four hours after completing the [18F]FDG scan (mean time: 4.2 hours), patients underwent a second PET scan using [18F]Sifalin-Tate at a standard administered activity of 3.0 MBq/kg.
3. Image Reconstruction and Analysis: PET images were reconstructed using standard clinical protocols, focusing on assessing potential residual [18F]FDG activity and its impact on SSTR-PET results. Organs such as the myocardium and tumor lesions were specifically analyzed for activity concentrations (ACTs) to estimate any residual [18F]FDG impact during the second PET scan.

Results

The study revealed that, in tissues with high physiological glucose metabolism but no physiological SSTR expression (e.g., the myocardium and brain), residual [18F]FDG activity during the [18F]Sifalin-Tate scan was negligible. Furthermore, simulations indicated that even when accounting for possible increases in FDG uptake over time, the residual FDG activity only accounted for approximately 6.8% of the activity concentrations measured in the tumor lesions during the second PET scan. This confirmed that any residual [18F]FDG activity had no significant impact on the quantification of [18F]Sifalin-Tate, even under a conservative analytical framework.

Findings from the dual-tracer PET/CT directly influenced treatment plans for 55% of the surveyed patients, demonstrating the significant value of dual-tracer imaging in improving therapy decisions.

Conclusions and Insights

This study demonstrates that long-axial field-of-view (LAFOV) PET scanners can facilitate a one-day dual-tracer imaging protocol while maintaining the semi-quantitative properties of two 18F-labeled radiotracers. This method simplifies the evaluation of tumor biology and reduces logistical challenges in clinical management. The findings highlight the clinical advantages of multi-tracer PET imaging, particularly for complex cases of neuroendocrine neoplasms.

In terms of clinical applications, the study’s methodology is extendable to other radionuclides and tumor types, offering significant potential to improve patient comfort and diagnostic efficiency.

Study Highlights

The key discovery of this study is the demonstration of the potential utility of dual-tracer PET/CT imaging in neuroendocrine tumors. Through the improved imaging precision afforded by LAFOV PET scanners and reduced radioactive dosages, the method provides more accurate treatment stratification for complex cases. Furthermore, the study presents a novel and effective framework that can significantly inspire future innovations in tumor imaging diagnostics.

This research offers new perspectives and tools for the clinical management of neuroendocrine tumors and serves as a paradigm for further investigations into advanced tumor imaging methodologies.