Neuroendocrine tumours (NETs) are a unique group of cancers that often require specialised imaging techniques for accurate diagnosis and monitoring. Unlike many other cancers, which can be detected using standard radiological imaging such as computed tomography (CT) or magnetic resonance imaging (MRI), NETs often require functional imaging to visualise their activity at the molecular level.
This is where nuclear medicine plays a critical role. Nuclear medicine imaging is not just about detecting the physical presence of a tumour—it also allows doctors to see how the tumour functions, including whether it expresses somatostatin receptors (SSTRs) or has a high metabolic rate. These insights are essential for staging the disease, selecting appropriate treatments, and monitoring response to therapy.
In this article, we explore the key nuclear medicine techniques used in NET diagnosis, their advantages over traditional imaging, and emerging advancements in this field.
Neuroendocrine Cancer Australia (NECA), is dedicated to assisting individuals diagnosed with NETs and their loved ones. NECA offers a wealth of resources, educational programs, and advocacy efforts aimed at deepening the understanding of NETs, improving patient care, and encouraging research advancements. Patients can engage with NECA’s comprehensive support and information by calling the NET nurse line.
Nuclear medicine is a specialised branch of medical imaging that uses radioactive tracers (radiopharmaceuticals) to diagnose diseases. Unlike standard imaging, which focuses on anatomy and structure, nuclear medicine provides information about how tissues and organs function.
In cancer diagnosis, nuclear medicine is particularly valuable because it allows doctors to:
Feature | Standard radiology (CT/MRI) | Nuclear medicine (PET/SPECT) |
Focus | Physical structure of tumours | Functional activity of tumours |
Best for | Assessing tumour size, shape, and spread | Identifying active tumour cells and receptor expression |
Contrast use | Uses iodine or gadolinium contrast | Uses radioactive tracers |
Limitations | May miss small, slow-growing NETs | Requires specialised tracers and imaging equipment |
Nuclear medicine plays an essential role in NET diagnosis because these tumours can be small, slow-growing, or spread widely, making them difficult to detect with conventional scans.
NETs often have somatostatin receptors (SSTRs), which allows them to be targeted using specific radiotracers in nuclear imaging. This enables:
One of the biggest challenges in NET diagnosis is that tumours often spread before symptoms appear. Nuclear medicine scans help:
By providing a whole-body view of NET activity, nuclear medicine scans offer a comprehensive assessment of the disease.
Gallium-68 DOTATATE PET/CT is the gold standard for imaging well-differentiated NETs. It works by:
Gallium-68 PET/CT has largely replaced older imaging techniques, offering higher resolution and better accuracy.
While Gallium-68 PET is effective for low and intermediate-grade NETs, high-grade, poorly differentiated neuroendocrine carcinomas (NECs) often do not express somatostatin receptors. Instead, they have high glucose metabolism, which makes fluorodeoxyglucose (FDG) PET/CT a better choice.
FDG PET/CT works by:
For some patients, both Gallium-68 PET and FDG PET may be needed to fully assess tumour behaviour. This dual imaging approach helps determine:
In some cases, individuals may have tumours with multiple different grades, making combined imaging particularly valuable for treatment planning.
Before the introduction of Gallium-68 PET/CT, Octreotide scans (Somatostatin Receptor Scintigraphy – SRS) were the main imaging method for NETs. They involve:
Most centres now prefer Gallium-68 PET/CT due to its greater accuracy and faster imaging time.
Here’s a cheat sheet on how to select the right nuclear medicine scan for NET diagnosis and treatment.
Imaging plays a crucial role in determining the extent of disease in patients with neuroendocrine tumours, helping to assess whether surgery is a viable option for tumour removal. It also identifies patients eligible for peptide receptor radionuclide therapy (PRRT) by evaluating somatostatin receptor (SSTR) expression and provides insight into lymph node and liver involvement for more effective treatment planning.
Ongoing imaging is equally important for monitoring response to therapies over time. By comparing scans taken before and after treatment, clinicians can track tumour shrinkage or progression, detect new metastases, and observe changes in tumour activity, allowing for timely adjustments to care.
Advancements in nuclear medicine are opening new possibilities for the diagnosis and treatment of neuroendocrine tumours (NETs).
Among the most promising developments is the introduction of new tracers like Copper-64 DOTATATE, which offers a longer half-life than the commonly used Gallium-68, allowing for more flexible imaging schedules and potentially improved diagnostic accuracy.
Alpha-emitting radiopharmaceuticals are also gaining attention for their ability to more precisely target NET cells, which may lead to better treatment outcomes and reduced damage to surrounding healthy tissue.
Looking ahead, the future of personalised imaging for NETs is set to benefit from rapid technological progress. Artificial intelligence is playing an increasingly important role in enhancing imaging interpretation, making it easier to detect tumours that might otherwise be missed.
At the same time, researchers are focusing on developing more tailored tracers designed to match the unique biological characteristics of different NET subtypes, offering a more individualised approach to patient care.
Access to Gallium-68 PET/CT and PRRT may be limited in some regions, requiring referral to NET specialist centres.
Early referral to a NET expert ensures the right imaging is used, improving diagnosis and treatment success.
Further information and support for people diagnosed with NETs is available by calling the NECA NET nurse line
SOURCES
Role of Nuclear Medicine in NET Diagnosis
