Neuroendocrine tumours (NETs) are a complex and diverse group of cancers that arise from neuroendocrine cells, which regulate various bodily functions through hormone production. Diagnosing and monitoring NETs can be challenging due to their small size, slow growth, and ability to develop in multiple organs. Unlike many other cancers, NETs often require specialised imaging techniques to confirm their presence, determine their extent, and guide treatment.
Radiological imaging plays a critical role in both initial diagnosis and ongoing management, helping clinicians assess tumour location, grade, spread, and response to therapy. With advancements in imaging technology, clinicians now have access to highly sensitive modalities that can detect even small, early-stage tumours, improving patient outcomes.
This article explores the key imaging techniques used for NET localisation, their strengths and limitations, and how emerging technologies are enhancing diagnostic accuracy.
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.
Imaging is essential for:
NETs often don’t form large masses, making them harder to detect than other cancers. Functional NETs secrete excessive hormones that cause symptoms, but non-functional secrete far less. NETs may remain undetected for years. Some NETs exhibit low metabolic activity, limiting their visibility on conventional imaging like CT or FDG PET scans.
Due to these factors, a combination of imaging techniques is often required for accurate localisation.
CT scans are a widely used imaging tool that provides detailed cross-sectional images of the body. They are particularly effective in:
Strengths:
Limitations:
MRI is often used as an alternative to CT, especially when evaluating soft tissue structures. It is particularly beneficial for:
MRI, especially contrast-enhanced MRI, is highly effective at detecting small liver metastases, which can be missed on CT. It is also useful for pancreatic NETs, where fine anatomical details are necessary for surgical planning.
Ultrasound is a non-invasive imaging technique that can sometimes detect NETs in the liver, pancreas, or intestines. However, it is generally less effective than CT or MRI for small tumours.
EUS is a highly specialised technique that allows for detailed imaging of pancreatic tumours by inserting an ultrasound probe into the gastrointestinal tract. This technique:
Gallium-68 DOTATATE PET/CT is considered the most effective imaging modality for NET detection. It uses a radiotracer that binds to somatostatin receptors on NET cells, allowing tumours to be visualised with high precision.
Unlike Gallium-68 DOTATATE PET, which targets well-differentiated, slow-growing NETs, FDG PET/CT is used to detect aggressive, high-grade neuroendocrine carcinomas (NECs).
Comparing FDG PET with Gallium-68 PET:
Before Gallium-68 PET was widely available, Octreotide scans (Somatostatin Receptor Scintigraphy – SRS) were the standard for NET imaging. This method:
Choosing the right imaging technique can have a vast impact on treatment.
How often imaging is recommended depends on the tumour’s grade, stability, and treatment history and your clinicians recommendations. For patients with stable, low-grade neuroendocrine tumours (NETs), scans are typically recommended every 6 to 12 months to monitor for any changes.
In cases involving progressing or high-risk tumours, imaging may be required more frequently, sometimes every 3 to 6 months, to track disease activity. After treatment—such as surgery or peptide receptor radionuclide therapy (PRRT)—regular follow-up imaging is essential to assess the response and watch for signs of recurrence.
Assessing treatment response and disease progression is a key reason for ongoing imaging. If scans show shrinking tumours, it suggests that the treatment is effective. When tumours remain stable, continued monitoring is often recommended to ensure they don’t begin to grow. The appearance of new metastases or changes in tumour activity may signal the need to adjust the treatment approach, such as switching therapies or exploring clinical trials.
There are several new technologies available for patients looking to combine imaging techniques.
Research continues to focus on enhancing imaging resolution and tracer specificity, allowing for even earlier detection and better treatment planning.
By utilising the right imaging modalities at the right time, clinicians can improve early diagnosis, treatment planning, and long-term monitoring of NETs.
Further information and support for people diagnosed with NETs is available by calling the NECA NET nurse line.
