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Treating GEP NE Tumours |
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About GEP NE Tumours
Gastro-entero-pancreatic neuroendocrine (GEP
NE) tumours are located in the digestive tract, primarily in the
gut (stomach or intestine) or the pancreas. GEP NE tumours produce
and secrete excessive amounts of hormones and other substances that
are normally regulated in the body in smaller amounts; the specific
hormones produced contribute to a person's symptoms.
The most common type of GEP NE tumour is a carcinoid
tumour. Carcinoid and pancreatic islet cell tumours produce
a variety of peptide
hormones and biogenic amines,
which vary by location and how they affect the body.
The types of GEP NE tumours include (listed in order of prevalence):
- Carcinoid tumours (55%), which arise from neuroendocrine cells
in the appendix (38%), ileum (23%), rectum (13%), and bronchus
(11.5%)
- Insulinomas (hypoglycaemic syndrome) (17%), an islet cell
tumour that secretes excess insulin, and may occasionally secrete
other hormones, including gastrin, ACTH and glucagons.
- Tumours of unknown type (15%)
- Gastrinomas (9%), a gastrin-releasing islet cell tumour of
the pancreas (50% to 60%) or duodenum (40% to 50%) that is associated
with Zollinger-Ellison syndrome
- Vasoactive intestinal peptide (VIP) tumours (VIPomas; Verner-Morrison
syndrome) (2%), an islet cell tumour of the pancreas, lung,
or ganglioneuromas that secretes an excess of VIP, a 28-amino
acid peptide. VIP plays a role in water transport in the gastrointestinal
tract, affects vascular tone, and acts as a local neurotransmitter
and modulating ion. More than 80% of VIPomas are malignant
- Glucagonomas, an islet cell tumour of the pancreas that secretes
an excess of glucagon, a 29-amino acid peptide
Neuroendocrine cell system of the gut
and pancreas
Gut
- ECL-cells (histamine, chromogranin A, and possibly gastrocalcin)
- G-cells (gastrin)
- S-cells (somatostatin)
- P-cells (unknown secretory product)
- EC-cells (serotonin, tachykinins, and chromogranin A)
- Peptidergic neurons and other neuroendrocrine cells
Pancreas
- ß-cell (insulin)
- α-cell (glucagon)
- D-cell (somatostatin)
- Common stem cells in the pancreatic ducts
- PP-cell (pancreatic polypeptide)
- D1 (unknown secretory product)
GEP NE tumours as a whole are rare, affecting only 1
to 2 people in 100,000. Carcinoid
syndrome caused by carcinoid tumours occurs in less than 10%
of people with carcinoid tumours, and affects 3 to 5 people
out of a million.
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Causes
Researchers have identified several genes that are involved in the development of GEP NE tumours, as well as various growth factors. |
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Symptoms
There are often no signs or symptoms in the early stages of GEP NE disease. When symptoms do occur, they usually are caused by the specific hormone that is produced by the tumour. The most common symptoms are diarrhoea and flushing. |
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Diagnosing
There are several types of GEP NE tumours, and each secretes different hormones that cause different symptoms, making diagnosis difficult. 1 A diagnosis can be based on symptoms as well as blood and urine tests that measure the amounts of certain hormones in the body.
The most common diagnostic test for carcinoid syndrome is a 5- hydroxyindoleacetic acid (5-HIAA) urine test. Foods that are rich in the chemical serotonin-for instance, bananas, pineapple, walnuts, pecans, and avocados-may increase 5-HIAA levels, resulting in a false-positive test.2 |
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Treatment
GEP
NE tumours may be treated with a combination of surgery, somatostatin
analogue therapy, chemotherapy, radiation therapy, and interferon
therapy. Surgical removal of the tumour may lead to symptom relief
or a cure. Synthetic forms of the brain hormone somatostatin,
such as octreotide, work at the site of the tumour. They bind to
sst-2/sst-5 receptors to regulate gastrointestinal hormone secretion
and affect tumour growth .3-5
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Case Studies
Case studies illustrate the challenges of diagnosing GEP NE tumours and carcinoid syndrome. |
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