How Theranostics is Transforming Neuroendocrine Cancer Treatment
- Jul 21
- 8 min read
Updated: Aug 5
Neuroendocrine tumours, commonly known as NETs, are a diverse group of uncommon cancers that develop from neuroendocrine cells. These specialised cells are found throughout the body and share characteristics of both nerve cells and hormone-producing endocrine cells.
NETs can behave very differently. Some grow slowly over many years, while others are more aggressive. Certain NETs produce excess hormones that cause noticeable symptoms, while others may cause few symptoms until they have grown or spread.
Theranostics is changing how some NETs are detected, assessed and treated. By combining molecular imaging with targeted radionuclide therapy, it can help clinicians identify disease throughout the body, confirm whether a treatment target is present and deliver radiation directly to tumour cells expressing that target.
For eligible patients with certain advanced NETs, this treatment approach is known as peptide receptor radionuclide therapy, or PRRT.
What Are Neuroendocrine Tumours?
Neuroendocrine cells help regulate functions throughout the body by receiving signals from the nervous system and releasing hormones.
When these cells begin to grow abnormally, a neuroendocrine tumour may develop.
NETs are classified according to factors including:
• Where the tumour originated
• Whether it produces hormones
• How quickly it is growing
• How closely the tumour resembles normal neuroendocrine cells
• Whether it has spread
• Which receptors or molecular targets it expresses
These characteristics help clinicians determine how the tumour is likely to behave and which treatments may be appropriate.
Where Are NETs Located?
Neuroendocrine tumours can develop in many parts of the body, but they most commonly arise in the gastrointestinal tract, pancreas or lungs.
Gastrointestinal Tract
Gastrointestinal NETs may develop in the:
Stomach
Small intestine
Appendix
Colon
Rectum
Some gastrointestinal NETs were historically called carcinoid tumours, although the term NET is now generally preferred.
Pancreas
Pancreatic neuroendocrine tumours develop from neuroendocrine cells within the pancreas.
They are different from pancreatic adenocarcinoma, the most common form of pancreatic cancer, and may require a different treatment approach.
Lungs
NETs may also arise in the lungs. These include typical and atypical lung carcinoid tumours.
More aggressive neuroendocrine lung cancers, such as small-cell lung cancer, generally behave differently and are treated using different approaches.
Other Locations
Less common neuroendocrine tumours include pheochromocytomas and paragangliomas.
Merkel cell carcinoma is a rare neuroendocrine skin cancer, but it is biologically distinct from the NETs most commonly considered for somatostatin receptor imaging and PRRT.
Are All NETs the Same?
No. NETs are a varied group of cancers rather than a single disease.
Some are well differentiated, meaning the cancer cells retain many features of normal neuroendocrine cells. These tumours often grow more slowly, although they can still spread and require treatment.
Other neuroendocrine cancers are poorly differentiated and may grow more rapidly. These are often classified as neuroendocrine carcinomas and may be treated differently.
Clinicians may assess the tumour’s:
Primary location
Stage
Grade
Differentiation
Ki-67 index, which measures how actively cells are dividing
Hormone production
Receptor expression
What Are the Symptoms of NETs?
Symptoms depend on where the tumour is located, whether it has spread and whether it produces excess hormones.
Some NETs cause few symptoms in their early stages. Others may cause symptoms that resemble more common conditions, which can sometimes delay diagnosis.
General symptoms may include:
Unexplained weight loss
Fatigue
Abdominal pain
Diarrhoea
Changes in bowel habits
Reduced appetite
Nausea or vomiting
A persistent cough or breathing changes
A lump or swelling
These symptoms can have many causes and do not necessarily indicate cancer. Persistent or unexplained symptoms should be discussed with a healthcare professional.
Hormone-Related Symptoms
NETs that produce excess hormones are known as functional NETs.
Possible symptoms may include:
• Facial flushing
• Diarrhoea
• Wheezing
• Shortness of breath
• Rapid heartbeat
• Shaking or sweating
• Dizziness
• Changes in blood glucose
• Excessive thirst
Carcinoid syndrome may occur when certain NETs release hormones into the bloodstream. Common symptoms include flushing, diarrhoea, abdominal cramping and wheezing.
How Are NETs Diagnosed?
Diagnosing a NET may involve several tests, including:
Blood and urine tests
Hormone or biomarker testing
CT or MRI scans
Ultrasound
Endoscopy
PET or other molecular imaging
Biopsy
A biopsy provides important information about the tumour type, grade and rate of growth.
Molecular imaging can provide additional information about the tumour’s biological characteristics and whether specific treatment targets are present.
What Treatment Options Are Available?
Treatment is highly individualised and depends on the tumour’s location, grade, stage, rate of growth, hormone activity and molecular characteristics.
A patient may receive one treatment or several treatments over time.
Surgery
Surgery may be used to remove a localised NET and can sometimes provide long-term disease control.
In selected cases, surgery may also reduce tumour burden or help manage symptoms when all disease cannot be removed.
Somatostatin Analogues
Many well-differentiated NETs express somatostatin receptors.
Somatostatin analogue medicines may help control hormone-related symptoms and slow tumour growth in some patients.
Targeted Therapies
Targeted medicines may be used to interfere with pathways involved in cancer growth and survival.
Their suitability depends on the type and characteristics of the NET.
Chemotherapy
Chemotherapy may be appropriate for some pancreatic NETs, faster-growing tumours or high-grade neuroendocrine cancers.
Radiation Therapy
External beam radiation therapy may be used to treat disease in a particular area, relieve symptoms or manage cancer that has spread to sites such as the bones.
Liver-Directed Treatments
When disease is concentrated in the liver, specialised procedures such as embolisation or ablation may be considered.
Peptide Receptor Radionuclide Therapy
PRRT is a targeted radionuclide therapy used for eligible patients with certain NETs.
It combines a molecule that binds to receptors on tumour cells with a therapeutic radioisotope.
Before treatment, molecular imaging is used to confirm that the relevant receptors are present.
How Does Theranostics Work for NETs?
The word theranostics combines: Therapy + Diagnostics
In NETs, one of the most established theranostic approaches targets the somatostatin receptor.
Many well-differentiated NET cells express high levels of these receptors, particularly somatostatin receptor subtype 2. This allows the same biological target to be used for both imaging and treatment.
Step 1: Molecular Imaging
The patient receives a small amount of a radioactive diagnostic agent designed to bind to somatostatin receptors.
A specialised PET scan can then show where the agent has accumulated throughout the body.
This may help clinicians:
Locate the primary tumour
Detect areas where cancer has spread
Assess the extent of disease
Confirm somatostatin receptor expression
Determine whether PRRT may be appropriate
Step 2: Targeted Treatment
If imaging confirms sufficient receptor expression and other eligibility requirements are met, PRRT may be considered.
A similar targeting molecule is combined with a therapeutic radioisotope, such as lutetium-177.
The treatment travels through the bloodstream, attaches to somatostatin receptors on tumour cells and delivers radiation to those cells and their immediate surroundings.
The aim is to damage cancer cells and slow disease progression while reducing exposure to tissues that do not express the target.
However, targeted treatment does not mean healthy tissue is completely unaffected. Some organs may naturally express somatostatin receptors or be involved in clearing the treatment, which is why kidney protection and ongoing monitoring are important.
What Is Lutetium-177 PRRT?
Lutetium-177 PRRT is an established treatment for eligible patients with certain somatostatin receptor-positive NETs.
The treatment uses a somatostatin analogue linked to lutetium-177. The targeting molecule binds to somatostatin receptors, allowing radiation to be delivered to tumour cells.
Not every person with a NET is suitable for PRRT.
Eligibility may depend on:
• The type, grade and location of the tumour
• Somatostatin receptor expression
• The extent of disease
• Previous treatments
• Kidney, liver and bone marrow function
• Overall health
• Treatment availability
Suitability should be assessed by an experienced multidisciplinary healthcare team.
How Is PRRT Administered?
PRRT is generally delivered in a hospital or specialised nuclear medicine centre.
Before treatment, patients may undergo blood tests, imaging and assessments of kidney, liver and bone marrow function.
On the day of treatment, an amino acid solution is usually given to help protect the kidneys. The therapeutic agent is then administered through a vein under the supervision of a nuclear medicine team.
The complete appointment may take several hours, including preparation, treatment, monitoring and radiation-safety checks.
A commonly used treatment schedule involves up to four cycles approximately eight weeks apart. However, the number and timing of treatments may vary according to the patient, treatment protocol and clinical response.
Many patients can return home the same day once radiation levels meet the required safety limits. The treatment centre will provide temporary radiation-safety instructions regarding close contact with other people.
Blood tests and follow-up imaging are used throughout the treatment course to monitor safety and response.
What Are the Potential Side Effects?
PRRT can cause side effects, although their type and severity vary between patients.
Possible side effects include:
Nausea or vomiting
Fatigue
Reduced appetite
Abdominal discomfort
Temporary changes in taste
Mild hair thinning
Reduced blood cell counts
Anaemia
Low white blood cell levels
Low platelet levels
Nausea may sometimes be related to the amino acid solution given to protect the kidneys.
Less common but potentially serious effects may include kidney impairment, persistent changes in blood cell counts and rare bone marrow conditions.
The risk of side effects may be influenced by previous treatments, kidney and bone marrow function, the extent of disease and the total amount of radiation administered.
What Are the Potential Benefits?
Theranostics may provide several benefits for eligible patients with somatostatin receptor-positive NETs.
More Accurate Disease Assessment
Molecular imaging can show disease throughout the body and provide information about receptor expression.
Better Detection of Metastases
Specialised imaging may identify disease that has spread beyond the primary tumour.
Treatment Selection Based on Biology
Imaging confirms whether the required target is present before treatment is considered.
Targeted Treatment for Advanced Disease
PRRT may provide an additional treatment option for certain advanced NETs that cannot be removed surgically or have progressed following other treatments.
Treatment of Disease in Multiple Locations
Because PRRT circulates through the bloodstream, it can target receptor-positive disease in several areas of the body.
Theranostics is not appropriate for every patient, and potential benefits must be considered alongside possible risks and other treatment options.
Is PRRT Available in Australia?
Lutetium-177 PRRT is available in Australia for eligible patients with certain NETs.
Access may depend on:
Tumour type and receptor expression
Previous treatments
Clinical eligibility
Treatment location
Funding arrangements
Availability of specialist services
PRRT is generally delivered through specialised hospitals and nuclear medicine centres.
Clinical trials are also investigating new radionuclides, treatment combinations, dosing approaches and applications for other types of neuroendocrine cancer.
The Role of Multidisciplinary Care
NET diagnosis and treatment often involve healthcare professionals from several specialties, including:
Medical oncologists
Nuclear medicine physicians
Surgeons
Endocrinologists
Gastroenterologists
Respiratory physicians
Radiologists
Radiation oncologists
Pathologists
Specialist nurses and allied health professionals
This multidisciplinary approach helps ensure that treatment decisions consider the tumour’s biology, available evidence and the individual patient’s needs.
The Key Takeaways
Neuroendocrine tumours are a diverse group of cancers that vary in their location, biology and rate of growth.
Theranostics has introduced a highly specialised approach for some NETs by connecting molecular imaging with targeted radionuclide therapy.
Somatostatin receptor imaging can help clinicians locate disease, assess whether the required treatment target is present and determine whether PRRT may be suitable. If eligibility criteria are met, a matched therapeutic agent can deliver radiation to tumour cells expressing that receptor.
For eligible patients with certain advanced NETs, PRRT may provide an important treatment option as part of a broader, personalised cancer care pathway.
However, it is not suitable for every NET or every patient. Treatment decisions should always be made in consultation with an experienced multidisciplinary healthcare team.
