Prostate Neuroendocrine Cancer

Overview

Prostate neuroendocrine cancer, also referred to as neuroendocrine prostate cancer (NEPC), is a rare and aggressive variant of prostate cancer that develops from or transforms into neuroendocrine cells within the prostate gland. It accounts for less than 2 per cent of all prostate cancers when it arises as a primary neuroendocrine cancer, though neuroendocrine features can also be found in a proportion of advanced prostate adenocarcinomas.

Unlike the most common form of prostate cancer, which grows in response to male sex hormones (androgens) and can be monitored using prostate-specific antigen (PSA) blood tests, NEPC behaves very differently. It grows independently of androgens, meaning standard hormone therapies are often less effective at controlling its growth. It also often does not produce significant amounts of PSA, making it harder to track with the usual blood tests used to monitor prostate cancer.

NEPC is important to understand not only as a rare primary condition but also because it can develop in some men with conventional prostate cancer after long-term hormone-based treatments. In these cases, prostate cancer cells can adapt over time, developing neuroendocrine features that allow the cancer to continue growing despite hormone therapy.

At NeuroEndocrine Cancer Australia (NECA), we support people living with prostate neuroendocrine cancer and their families through education, resources, advocacy, and access to the NET Nurse, Counsellor and Dietitian services.

Understanding prostate neuroendocrine cancer

The prostate gland contains a small population of neuroendocrine cells alongside the glandular (secretory) cells that are the origin of common prostate adenocarcinoma. These neuroendocrine cells help communication between cells in the prostate by releasing signalling substances that influence local tissue function.

NEPC arises from or transforms into these neuroendocrine cells and, as a result, behaves very differently from the adenocarcinoma that accounts for the vast majority of prostate cancers. The key biological distinction is androgen independence: NEPC does not rely on testosterone or other androgens to grow and, accordingly, does not respond to androgen deprivation therapy (ADT) or the newer androgen receptor pathway inhibitors that are central to treating metastatic prostate adenocarcinoma.

This androgen independence also means NEPC cells typically do not express prostate-specific antigen (PSA) at significant levels. A patient with NEPC may experience rapid cancer progression and spread while their PSA blood test results remain completely normal or near-normal, which can lead to a delayed recognition of disease activity if PSA is the only marker being monitored.

Instead of PSA, NEPC tumours frequently produce elevated levels of alternative markers including Chromogranin A (CgA) and Neuron-Specific Enolase (NSE), which may be elevated in some patients.

NEPC is characterised by rapid growth, an aggressive pattern of spread including to visceral organs such as the liver and lungs, as well as to the bones, and a generally poor prognosis compared to conventional prostate adenocarcinoma.

How prostate neuroendocrine cancer develops

NEPC develops through two distinct pathways.

1. Treatment-induced NEPC (t-NEPC)

Treatment-induced NEPC is the most common clinical form of NEPC. It occurs when prostate adenocarcinoma cells undergo a process called lineage plasticity, a process where cancer cells change their characteristics and acquire neuroendocrine features.This adaptation allows some cancer cells to survive and continue growing despite therapies that target androgen signalling.

This transformation is particularly associated with long-term androgen deprivation therapy and with the newer and more potent androgen receptor pathway inhibitors used to treat metastatic castration-resistant prostate cancer. Approximately 10 to 17 per cent of men with metastatic castration-resistant prostate cancer develop t-NEPC after extended hormone therapy.

The transformation is typically driven by the loss of key tumour suppressor genes, particularly TP53 and RB1, alongside the upregulation of cellular growth drivers such as MYCN (a gene involved in cell proliferation) and Aurora Kinase A. These molecular changes contribute to treatment resistance by allowing prostate cancer cells to become less dependent on androgen signalling and acquire aggressive neuroendocrine features.

1. De novo NEPC

De novo NEPC is far rarer, accounting for less than 1 per cent of all prostate cancer diagnoses. It arises directly as a neuroendocrine cancer within the prostate without any prior history of adenocarcinoma or hormone therapy. This form can include well-differentiated neuroendocrine tumours (carcinoids), which generally have a more favourable outlook, as well as high-grade poorly differentiated neuroendocrine carcinomas.

Causes of prostate neuroendocrine cancer

The exact initial causes of prostate neuroendocrine cancer are not fully understood. In the case of de novo NEPC, the tumour arises from neuroendocrine cells in the prostate through mechanisms that remain under investigation.

In treatment-induced NEPC, the process is better characterised. Extended use of androgen deprivation therapy and androgen receptor pathway inhibitors creates a selective environment in which prostate cancer cells that can survive without androgen signalling gain a survival advantage. This selective pressure can promote epigenetic and genetic changes that allow prostate adenocarcinoma cells to reprogram their identity from glandular to neuroendocrine.

Key molecular drivers associated with this transformation include:

• Loss of TP53 (a tumour suppressor gene that normally prevents uncontrolled cell growth)
• Loss of RB1 (a tumour suppressor gene involved in regulating cell cycle)
• Amplification or overexpression of MYCN (a gene that drives rapid cell proliferation)
• Overexpression of Aurora Kinase A (which cooperates with MYCN to promote neuroendocrine differentiation)
• Epigenetic changes driven by EZH2, a protein that can silence tumour suppressor genes

Understanding these molecular drivers has opened new avenues for targeted therapeutic investigation.

Subtypes of prostate neuroendocrine cancer

Several distinct subtypes of prostate neuroendocrine cancer exist, each with different clinical features and prognosis.

Small cell neuroendocrine carcinoma of the prostate

This is the most common and most aggressive form of NEPC. It closely resembles small cell carcinoma of the lung at the molecular and clinical level, and treatment strategies have been adapted from that setting. Small cell neuroendocrine carcinoma of the prostate grows and spreads extremely rapidly.

Large cell neuroendocrine carcinoma of the prostate

This is a rare high-grade variant with large sheets of poorly differentiated neuroendocrine cells. Like small cell carcinoma, it carries a poor prognosis.

Adenocarcinoma with focal neuroendocrine differentiation

In some prostate adenocarcinomas, small clusters of neuroendocrine-like cells are interspersed within an otherwise typical adenocarcinoma. This is a relatively common finding in advanced prostate cancer, particularly after hormone therapy, and its clinical significance varies. Some clinicians consider this a precursor or early manifestation of lineage transformation.

Well-differentiated neuroendocrine tumour (carcinoid) of the prostate

This is an extremely rare form of prostate neuroendocrine tumour and behaves more similarly to neuroendocrine tumours in other organs. Their growth rate varies according to tumour grade, but they generally have a more favourable prognosis than the high-grade neuroendocrine carcinoma subtypes.

Effects of prostate neuroendocrine cancer on the body

Prostate neuroendocrine cancer has a range of effects that differ from conventional prostate adenocarcinoma, reflecting both its distinct neuroendocrine biology and clinical behaviour.

The most significant effect is the rapid development and spread of metastatic disease. NEPC shows a particular tendency to spread to visceral organs including the liver and lungs, in addition to the bones and lymph nodes that are more typical metastatic sites for prostate adenocarcinoma. Brain metastases are also more common than in conventional prostate cancer.

Because PSA production is low or absent, the disease can progress significantly before standard PSA-based monitoring raises the alarm. This can result in a delayed recognition of relapse or treatment resistance in men who developed NEPC from prior adenocarcinoma.

Paraneoplastic syndromes

Although uncommon, some NEPCs secrete hormones or other bioactive substances that cause systemic effects, which may occur before the tumour is identified on imaging. These are known as paraneoplastic syndromes and can include:

• Cushing’s syndrome, caused by ectopic adrenocorticotropic hormone (ACTH) secretion from tumour cells stimulating excess cortisol production, which may lead to rapid weight gain, high blood pressure, muscle weakness, and fluid retention
• SIADH (syndrome of inappropriate antidiuretic hormone secretion), which causes the body to retain excess water, dangerously diluting blood sodium levels and causing confusion, lethargy, and in severe cases, seizures
• Carcinoid-like symptoms in rare cases, including flushing, diarrhoea, or wheezing related to secretion of serotonin or other bioactive peptides, although this is very uncommon in prostate neuroendocrine cancer.

The occurrence of any of these syndromes in the context of prostate cancer should prompt investigation for neuroendocrine transformation or de novo NEPC.

Symptoms of prostate neuroendocrine cancer

Symptoms of NEPC broadly resemble those of advanced prostate adenocarcinoma but typically progress far more rapidly. The urgency and speed of symptom development is often a clinical clue to neuroendocrine involvement.

Urinary symptoms may include:

• Weak or interrupted urinary stream
• Difficulty starting urination
• Frequent urination, particularly at night
• Painful urination

Symptoms related to spread and systemic disease may include:

• Severe or rapidly worsening bone pain, particularly in the spine, hips, and pelvis
• Discomfort sitting or moving
• Unexplained weight loss and fatigue
• Blood in the urine or seminal fluid
• Symptoms of visceral metastases such as abdominal swelling or pain (liver involvement) or shortness of breath (lung involvement)

As noted above, paraneoplastic syndromes may also cause symptoms including sudden severe hypertension, muscle weakness and in Cushing’s syndrome, or fluid retention, and confusion in SIADH due to low blood sodium levels (hyponatraemia).

In men with known prostate adenocarcinoma on hormone therapy, a pattern of rapid clinical deterioration with low or stable PSA should raise clinical suspicion for neuroendocrine transformation.

Diagnosis of prostate neuroendocrine cancer

Diagnosing NEPC requires a high level of clinical suspicion, tissue biopsy, and specialised pathological evaluation. Standard prostate cancer tests are insufficient.

1. Clinical assessment and PSA context

In men with a history of prostate adenocarcinoma, suspicion for NEPC is raised when there is rapid clinical deterioration or rising symptoms despite low or stable PSA, or when disease continues to progress despite hormone therapy.

In de novo presentations, NEPC is typically identified after biopsy of an identified prostate mass or a metastatic lesion.

2. Tissue biopsy and immunohistochemistry

Definitive diagnosis requires tissue biopsy of the prostate or a metastatic site. The pathologist examines the structural appearance of the cells and uses specialised immunohistochemical stains to confirm neuroendocrine origin.

Key diagnostic markers include:

• Chromogranin A: neuroendocrine marker that is often expressed in well-differentiated neuroendocrine tumours but may be absent in poorly differentiated neuroendocrine carcinomas.
• Synaptophysin: a neuroendocrine marker expressed in most NEPCs
• CD56: another neuroendocrine marker that may be expressed in NEPC s
• Low or absent expression of androgen receptor (AR) and PSA

These markers distinguish NEPC from prostate adenocarcinoma and confirm the neuroendocrine phenotype.

3. Blood markers

Serum Chromogranin A and Neuron-Specific Enolase (NSE) are measured as they can be elevated in some cases of NEPC and can help assess disease extent and monitor treatment response. PSA remains important to measure but low levels should not be taken as reassuring in the context of suspected NEPC.

Appropriate investigations for paraneoplastic syndromes (including ACTH, cortisol, sodium levels) are also ordered when clinically indicated.

4. Advanced imaging

CT scanning of the chest, abdomen, and pelvis is used to assess for metastatic disease and to detect visceral spread.

Because NEPC tumours often show reduced or absent PSMA expression but may express somatostatin receptors (particularly SSTR2), imaging strategy may differ from that used for typical prostate cancer. In men where neuroendocrine transformation is suspected, clinicians may consider:

• PSMA PET/CT: areas that show low or absent PSMA expression despite active disease may indicate neuroendocrine differentiation
• Gallium-68 DOTATATE PET/CT: identifies tumours expressing somatostatin receptors, which is relevant both for staging and for identifying eligibility for somatostatin receptor-targeted treatments.

Differing imaging findings, where lesions are PSMA-negative but DOTATATE-positive, may indicate areas of neuroendocrine differentiation or transformation. These findings can help identify lesions for targeted biopsy to confirm the diagnosis and guide personalised treatment planning.

MRI, bone scan, and other investigations are used as clinically indicated.

Treatment options for prostate neuroendocrine cancer

Because NEPC grows independently of androgens, standard hormone therapies including androgen deprivation therapy and androgen receptor pathway inhibitors are not effective against the neuroendocrine component. Treatment is instead directed at the aggressive biology of the neuroendocrine cells themselves.

A specialist multidisciplinary team including a urologist, medical oncologist, radiation oncologist, nuclear medicine specialist, and palliative care clinician should guide treatment planning.

Platinum-based chemotherapy

The main treatment for high-grade NEPC, particularly small cell neuroendocrine carcinoma, using platinum-based chemotherapy together with etoposide. This treatment is similar to that used for small cell lung cancer because the two cancers share many biological and clinical characteristics, and there is limited research specifically for NEPC.

Chemotherapy can help control symptoms and slow progression but is rarely curative in the metastatic setting, and responses are often not durable.

Managing the adenocarcinoma component

In men with t-NEPC arising from prior adenocarcinoma, some elements of androgen receptor-targeted therapy may be continued to control any residual adenocarcinoma component alongside chemotherapy addressing the neuroendocrine component.

PRRT and somatostatin receptor-targeted approaches

For NEPC tumours that express somatostatin receptors on Gallium-68 DOTATATE imaging, peptide receptor radionuclide therapy (PRRT) with Lutetium-177 DOTATATE may be considered. Although PRRT is not currently a standard treatment for NEPC, early studies suggest it may benefit some patients with well-selected, somatostatin receptor-positive disease. Clinical trials are ongoing to better define its role, and eligibility should be discussed with the treating specialist team.

Targeted therapies and emerging treatments

Active research is investigating several novel approaches to NEPC:

• DLL3-targeted therapies: Delta-like ligand 3 (DLL3) is a surface protein overexpressed in a substantial proportion of NEPC tumours while being largely absent in healthy tissues. Bispecific T-cell engager antibodies targeting DLL3 are in clinical trials and have shown early signals of activity.
• DLL3-targeted radioligand therapies: Experimental radioligands that deliver targeted radiation directly to DLL3-expressing cells are in development.
• EZH2 inhibitors: EZH2 is an epigenetic regulator that may drive the transformation from adenocarcinoma to neuroendocrine phenotype. Inhibiting EZH2 is being studied as a way to block this transformation.
• Combination approaches: Trials are exploring combinations of chemotherapy, targeted agents, immunotherapy, and radioligand therapy.

Access to novel treatments is typically through clinical trials. The treating team can advise on currently open trials.

Palliative and supportive care

Given the nature of NEPC can be aggressive and the frequent challenges in achieving durable disease control, high-quality palliative and supportive care is an essential part of management. This includes pain management, bone-targeted treatments for skeletal metastases, management of urinary symptoms, and psychological and practical support for patients and families.

Living with prostate neuroendocrine cancer

Prostate neuroendocrine cancer is a challenging diagnosis, both because of its aggressive nature and because it often develops in men who have already been managing prostate cancer for some time. For those in whom NEPC has emerged as a form of treatment resistance, there is often a significant psychological impact associated with the shift to a different and more aggressive cancer biology.

Coping with rapid disease progression, complex treatment regimens, and uncertainty about the future requires strong emotional and practical support. Connecting with specialist care, peer support, and clear and reliable information are all important aspects of wellbeing.

Dietary considerations

There are no specific dietary restrictions associated with NEPC in general. However, men on systemic chemotherapy or experiencing symptoms such as diarrhoea, nausea, or weight loss may benefit significantly from dietetic assessment and guidance. Those with paraneoplastic syndromes affecting fluid balance or electrolytes require specific dietary and medical management as directed by their treating team.

NeuroEndocrine Cancer Australia provides access to a specialist NET dietitian as part of its support services.

Monitoring symptoms

Men living with NEPC should monitor for any new or worsening symptoms and report them promptly to their treating team. Given that PSA may not reflect disease activity, monitoring relies more heavily on symptom reporting, clinical examination, serum CgA and NSE measurements, and imaging.

Symptoms such as new or worsening bone pain, abdominal swelling, shortness of breath, confusion, severe fluid retention, or rapidly worsening fatigue should always be evaluated promptly.

Supportive care and resources

Living with NEPC requires specialist multidisciplinary support alongside strong emotional and practical resources. NeuroEndocrine Cancer Australia provides education, resources, advocacy, and access to specialist services for people affected by prostate neuroendocrine cancer and their families, including the NET Nurse service and specialist NET counsellor and dietitian.

Research and future directions

Research into prostate neuroendocrine cancer is advancing rapidly, driven by growing understanding of the molecular mechanisms of neuroendocrine transformation and the development of new diagnostic tools and therapeutic targets.

Ongoing studies and clinical trials

Clinical trials are investigating DLL3-targeted therapies including bispecific T-cell engager antibodies, DLL3-targeted radioligand therapies, EZH2 inhibitors, PRRT for SSTR2-expressing NEPC, and various combination approaches. Australia participates in international clinical trial networks for advanced prostate cancer and neuroendocrine cancers.

People with NEPC should ask their treating team whether any currently open clinical trials are available to them, as trial participation may offer access to novel therapies beyond standard options.

Prostate neuroendocrine cancer is one of the most challenging variants of both prostate cancer and neuroendocrine cancer. Specialist multidisciplinary care, timely recognition of neuroendocrine transformation in men on hormone therapy, access to emerging treatments and clinical trials, and strong supportive care are all essential to optimising outcomes and quality of life.

For patients diagnosed with prostate neuroendocrine cancer, contact NeuroEndocrine Cancer Australia for comprehensive support and information through our NET Nurse service.