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Prostate Neuroendocrine Tumours

Prostate neuroendocrine tumours (NETs), also known as carcinoid tumours of the prostate, are a very rare type of neuroendocrine tumour that develops in the prostate gland.

The prostate is a walnut-shaped gland in the male reproductive system. It sits below the bladder, and in front of the rectum (end of the small bowel). The prostate is responsible for producing semen, a bodily fluid that acts as a vessel for sperm transport during ejaculation, and nourishment to keep the sperm alive outside of the body. It also has a small role in the urinary system, as the thin tube (ureter) that runs through the bladder to the penis is passed through the prostate.

Neuroendocrine cancers are a complex group of tumours that develop in the neuroendocrine system, which is responsible for regulating important bodily functions such as heart rate, blood pressure and metabolism. They most commonly develop in the gastro-intestinal tract, pancreas, and the lungs; however, they can develop anywhere in the body. These tumours develop from neuroendocrine cells, which are responsible for receiving signals from the nervous system and producing hormones and peptides (small proteins) in response.

Prostate NETs are most commonly found in men over 55 years of age. However, anyone with a prostate – including teenagers, transgender women, non-binary individuals, and intersex people – can develop this disease at any age.

Types of Prostate Neuroendocrine Tumours

Because of how rare prostate NETs are, there has been limited research done into the types of this disease. However, some distinct subtypes have been identified.

Well-Differentiated Neuroendocrine Tumour of the Prostate

Well-differentiated neuroendocrine tumours of the prostate is a very rare form of cancer that are characterised by relatively ‘normal looking’ cells under the microscope. This subtype is often associated with multiple endocrine neoplasia type 2B (MEN2B). Well-differentiated neuroendocrine tumours of the prostate are often categorised as low-grade (slow growing), however can metastasise if left untreated.

Neuroendocrine Carcinomas of the Prostate

Neuroendocrine carcinomas of the prostate are a rare type of cancer that are characterised by abnormal looking cancer cells under the microscope. There are two primary subtypes of this disease.

Small Cell Carcinoma of the Prostate

Small cell neuroendocrine carcinoma of the prostate is a very rare form of cancer that is often associated with adenocarcinomas of the prostate. This type of tumour is often classified as a type of extrapulmonary small cell lung cancer, as the cells present are identical under a microscope. Unfortunately, small cell neuroendocrine carcinomas of the prostate are often aggressive, and may not have as good of a prognosis as other types of prostate cancers.

Large Cell Carcinoma of the Prostate

Large cell neuroendocrine carcinoma of the prostate is a very rare form of cancer that is often associated with adenocarcinoma of the prostate. Unfortunately, large cell neuroendocrine carcinomas of the prostate are often aggressive, and may not have as good of a prognosis as other types of prostate cancers.

Adenocarcinoma with Neuroendocrine Differentiation

Adenocarcinoma with neuroendocrine differentiation is a very rare form of cancer that looks like an adenocarcinoma of the prostate under the microscope, but is positive for a neuroendocrine marker during biopsy and blood testing. Similarly to adenocarcinoma of the prostate, these types of tumours can be aggressive and metastasise, but can have a good prognosis when caught early.

Treatment-related neuroendocrine prostatic carcinoma (tNEPC) is a very rare form of cancer that develops after long-term androgen deprivation therapy (ADT). It is most commonly seen after treatment of small cell neuroendocrine carcinoma of the prostate or large cell neuroendocrine carcinoma of the prostate, and can be associated with adenocarcinoma of the prostate. Unfortunately, tNEPC is often aggressive, and may not have as good of a prognosis as other types of prostate cancer.

Treatment

If a prostate NET is detected, it will be staged and graded based on size, metastasis, and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.

Cancers can be staged using the TNM staging system:

  • T (tumour) indicates the size and depth of the tumour.
  • N (node) indicates whether the cancer has spread to nearby lymph nodes.
  • M (metastasis) indicates whether the cancer has spread to other parts of the body.

This system can also be used in combination with a numerical value, from stage 0-IV:

  • Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
  • Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
  • Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
  • Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
  • Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.

Cancers can also be graded based on the rate of growth and how likely they are to spread:

  • Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
  • Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
  • Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.

Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.

Treatment is dependent on several factors, including location, stage of disease and overall health.

Treatment options for prostate NETs may include:

  • Surgery, potentially including:
    • Prostatectomy.
    • Lymphadenectomy.
  • Chemotherapy.
  • Radiation therapy, potentially including:
    • Brachytherapy.
    • External beam radiation therapy (EBRT).
  • Hormone therapy, such as androgen deprivation therapy (ADT) – not recommended for treatment-related neuroendocrine prostatic carcinoma.
  • Clinical trials.
  • Palliative care.

Prostate Neuroendocrine Tumour Treatment and Fertility

Treatment for prostate NETs may make in difficult to conceive a child. If fertility is important to you, discuss your options with your doctor and a fertility specialist prior to the commencement of treatment.

Risk factors

Because of how rare prostate NETs are, there has been little research done into the risk factors of this disease.

Symptoms

Some patients with prostate NETs will appear asymptomatic in the early stages of disease. As the tumour progresses, some of the following symptoms may appear:

  • Changes in urination, such as:
    • Polyuria.
    • Feeling like your bladder isn’t empty after urination.
    • Slow urine flow.
    • Weaker bladder.
    • Loss of bladder control.
  • Incontinence.
  • Blood in urine and/or semen.
  • Erectile dysfunction.
  • Pain when ejaculating.
  • Unexplained weight loss.
  • Bone pain.
  • Fatigue.
  • Carcinoid syndrome (rare), which carries its own set of symptoms:
    • Facial flushing (usually red or purple in the face, neck, and/or upper chest).
    • Diarrhoea.
    • Wheezing.
    • Abdominal pain.
    • Carcinoid heart disease (plaques on the heart muscle caused by excess hormone production).
    • Faecal urgency.
    • Fatigue.
    • Skin changes, such as red or purple spots on the face, neck, and/or upper chest.
  • Paraneoplastic syndromes (rare).
  • Hypercalcaemia (rare).

Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.

Diagnosis

If your doctor suspects you have a prostate NET, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment:

  • Physical examination.
  • Digital rectal examination (DRE).
  • Imaging tests, potentially including:
    • TRUS (transrectal ultrasound).
    • MRI (magnetic resonance imaging).
    • CT (computed tomography) scan.
  • Blood tests, such as to check your PSA level.
  • Urine tests.
  • Biopsy.

References

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