Neuroendocrine Tumours

Incidences of neuroendocrine tumours (NETs) in Canada have more than doubled in the last 15 years, and they have become the second-most prevalent tumours of the GI tract. They develop from cells of the neuroendocrine system located throughout the body, but especially in and around the stomach, bowel, and lungs. Neuroendocrine cells produce hormones that control the way organs work, and their tumours are classified according to the site of origin. Some examples include small bowel NET, appendiceal NET, stomach NET, or pancreatic NET. Often, they grow slowly, but they can also be aggressive and invade neighbouring organs (metastasize).

The exact cause of these tumours is not known, but people who suffer a condition called multiple endocrine neoplasia (MEN) are more prone to them.

Symptoms for this condition are usually not evident but, depending on the tumour morphology, signs of the disease might include:

  • Discomfort or pain in the abdomen.
  • Nausea and vomiting.
  • Diarrhea.
  • Blood in the stool.
  • Fatigue caused by anemia.
  • Stomach ulcers.
  • Blockage of the bowels.

Another variety of symptoms are suggestive of carcinoid syndrome, which occurs when the NET produces large secretions of serotonin and other chemicals. These symptoms include:

  • Flushing of the skin, mainly the face and neck.
  • Diarrhea.
  • Wheezing and difficulty breathing.
  • Fast or irregular heartbeat.
  • Low blood pressure.
  • Heart damage (carcinoid heart disease).[1]

When signs and symptoms suggest NET, diagnosis through a biopsy is mandatory. This is usually done during surgery or laparoscopy, and it is usually followed by immunological studies to determine the type (morphology) of tumour. Other diagnostic techniques consist of:

  • Complete blood cell count (CBC), plus levels of electrolytes and sugar in blood.
  • Urine tests to detect excessive levels of serotonin.
  • Ultrasound.
  • PET and CT scans measure cell activity using low-dose radiation, giving a clearer picture of the tumours.
  • MRI gives a more detailed and specific picture of the organs affected.
  • Radioactive scans (such as octreotide or metaiodobenzylguanidine (MIBG) scans) use radioactive materials that bind to the tumour cells, making them easier to identify. They can detect the site of origin, as well as possible metastasis.

Treatment for NETs will vary according to the site where they started, the size of the tumour and whether it has spread to other organs, the manifestation of carcinoid syndrome, and the morphology (appearance) of the cells under microscopy.

If the tumour is localized, surgery to remove it will be performed. In the case of carcinoid syndrome, there are drugs to counter the symptoms. These drugs may also control the growth of new NETs. Chemotherapy and targeted therapy are also effective at controlling tumour growth. Radiation therapy might be used to deal with metastasis.