Neuroendocrine Tumours (NETs)

The tumours may arise from specialised cells, which secrete specific chemicals (hormones). The oversecretion of these hormones can result in specific symptom complexes (syndromes), which can be attributed to the action of these hormones: 

• Functioning tumours: Tumours associated with the oversecretion of hormones and specific syndromes
• Non-functioning tumours: Tumours which do not secrete specific hormones 

Depending on their biology and aggressiveness, neuroendocrine tumours are classified into three grades:

• Grade 1 and 2 tumours: More benign and slow growing.
• Grade 3 tumours (neuroendocrine carcinomas): Locally aggressive and spread to other organs.

The symptoms differ based on the tumour type (functioning and non-functioning neuroendocrine tumours):

• Functioning neuroendocrine tumours 

  These secrete hormones which give rise to specific symptoms, based on the hormone secreted. Diagnosis is mainly based on clinical suspicion. Most common types include:

  • Insulinoma: Excess insulin leads to very low blood sugar (hypoglycaemia), causing sweating, confusion, or fainting.
  • Gastrinoma: Oversecretion of acid in the stomach, leading to severe acidity, ulcers in the stomach/intestine, and reflux-like symptoms. The lesion causing gastrinoma may be present within the pancreas or even in the small intestine (duodenum).
  • Carcinoid tumour: Produces serotonin (5 HT), leading to diarrhoea, flushing, and intermittent abdominal pain

• Non-functioning tumours

  These usually do not produce symptoms as they do not secrete hormones. Nevertheless, they may produce the following symptoms:

  • Bleeding: Presents as blood in vomit or dark stools (melena)
  • Anaemia (low haemoglobin), leading to weakness
  • Persistent abdominal pain
  • Loss of appetite and unexplained weight loss

The exact cause of neuroendocrine tumours is not fully known. The chances of tumour development increase in the following cases:

• Genetic mutation: Variations in the genes and a family history increase the risk
• Pre-existing conditions such as diabetes and peptic ulcers
• Rare inherited diseases such as neurofibromatosis, multiple endocrine neoplasia, and Von Hippel-Lindau syndrome
   

Doctors may use a combination of blood tests and imaging to confirm the diagnosis:

• Blood tests: Specific blood tests aim to identify elevated levels of the hormones in the blood, such as insulin, gastrin, chromogranin, etc.
• CT scan and imaging: Neuroendocrine tumours may be incidentally discovered during an ultrasound or CT scan performed for other reasons. Tumours have a characteristic appearance, which can raise suspicion of pancreatic neuroendocrine tumours.
• DOTA scan: This is a specialised type of nuclear medicine scan, specific and sensitive for neuroendocrine tumours. The presence of dye uptake confirms the presence of a tumour.

Treatment depends on the tumour type, size, and whether it has spread:

• Surgery (main treatment): Depending on the location of the tumour, the operation indicated would include removal of the affected organ with an adequate surrounding tissue (margin), which may include:

  • Whipple procedure or distal pancreatectomy for pancreatic tumours
  • Small bowel resection for the removal of a segment of intestine
  • Gastrectomy for stomach neuroendocrine tumours
  • Colectomy for removal of parts of the large intestine
  • Liver surgery (if the tumour spreads to the liver) can be potentially curative
• Observation: Small asymptomatic non-functioning neuroendocrine tumours may be kept under observation and surveillance only after thorough investigation and discussion.
• Non-surgical therapy
  • Chemotherapy: When surgery is not possible, certain medications are available, which will slow down the progression of the disease and also control the symptoms.
  • Somatostatin analogues: These cause inhibition of the release of hormones and hence, help in controlling the symptoms. The somatostatin analogues also prevent the spread of tumour.
  • Ablation: Radiofrequency ablation or microwave ablation is performed on the disease that has spread to the liver or any other organ (e.g. lung).

Seek medical attention if you experience persistent abdominal pain or bloating, unexplained weight loss, diarrhoea, recurrent low blood sugar spells, or blood in vomit or stools.

There is no definite way to prevent neuroendocrine tumours, but you can reduce risk by:

• Following a healthy diet rich in fruits and vegetables.
• Avoiding smoking and excess alcohol.
• Undergoing regular check-ups if you have a family history of genetic syndromes linked to neuroendocrine tumours.

For diagnosis and treatment of neuroendocrine tumours, patients may need to consult:

• Gastroenterologist for initial evaluation and diagnostic tests.
• Surgical oncologist/hepatobiliary surgeon for surgery if needed.
• Medical oncologist for chemotherapy or targeted drug therapy.
• Endocrinologist for hormone-related symptoms.