Diagnosis

NET cancers are difficult to diagnose. After the onset of symptoms, which are often nonspecific and vague, a diagnosis can take an average of 3 – 7 years. If NET cancers are detected early in their development, they can often be cured with surgery. At present, however, most NET cancers are diagnosed at a later stage, when they have already spread to other parts of the body. In these cases, they can rarely be cured, although the symptoms can often be managed successfully for a number of years.

Depending on where they are in the body, NET cancers can give rise to a wide variety of symptoms. These symptoms may be mild or nonspecific, and are often similar to those of other, more common conditions.

For example, many of the symptoms associated with carcinoid tumors are similar to those of Irritable Bowel Syndrome (IBS), Crohn’s disease, peptic ulcer disease, gastritis, other digestive disorders, asthma or pneumonia.

Many physicians are unfamiliar with NET cancers and therefore less likely to suspect a NET cancer in their initial investigations.

NET cancers are difficult to detect for a number of reasons:

  • Size – they are often small; some NET cancers can be less than a centimeter in size
  • Location – NET cancers can occur almost anywhere in the body
  • Symptoms – these can vary enormously, and some patients have no symptoms at all
  • Testing – there are many different types of NET cancer, and a series of specialized tests is necessary. A biopsy is a definitive tool for a NET cancer diagnosis.

Tests to help diagnose NET cancers

There are a number of different tests and scans which may be used to detect a NET cancer. Some of these tests work by looking for hormonal changes triggered by the cancerous cells, while others look for the tumor itself.

NB: There is no standard group of tests – each patient may need to undergo a different combination of tests. If you have any questions about these tests, please confer with your medical team.

Biopsy

This involves taking a piece of tissue from the suspect tumor and having it analyzed in the laboratory by a specialist called a histopathologist.

Specifically, in clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist, after the specimen has been processed and histological sections have been placed onto glass slides.

The pathologist may review the biopsy sample and give the tumor a proliferative index, i.e. a measure of the number of cells in the tumor that are dividing (proliferating). A proliferation index of less than 2% means that the tumor is very slow growing, while a value above 10% suggests faster growth. The test for determining a proliferation index is called Ki67 or MIB1.

Being able to look at the tumor under the microscope can be the only way to determine exactly what type of NET cancer it is.

Blood Tests

The patient may be asked to have a fasting gut hormone blood test, and blood will also be collected for a range of other tests. Doctors will be looking for certain NET markers, particularly chromogranin A and B, pancreatic polypeptides, insulin and gastrin, glucagon, neurotensin, VIP (vaso-intestinal peptide) and for evidence of a rise in certain peptides and hormones in the blood, as well as checking how well the kidneys and liver are functioning. If the results of these tests suggest the presence of a NET, further imaging tests should be carried out.

Other biochemical tests

  • A summary of other biochemical tests is listed below:
  • Full blood count
  • Kidney function tests (urea and electrolytes)
  • Liver function tests
  • Thyroid function tests
  • Pituitary hormone screen, e.g. adrenocorticotropic hormone (ACTH), prolactin, growth hormones and cortisol
  • Serum calcium, parathyroid hormone levels (in all pancreatic NET patients, as a simple screening test for MEN-1 syndrome)

Urine Tests

5-HIAA (hydroxyindoleacetic acid) is a substance that is naturally passed out by the body. Normally, only small amounts are present in the urine. Elevated levels in a urine sample may indicate a NET, although further tests are required to confirm the diagnosis. This test can also be negative even if a person has a NET cancer, and further testing is essential.

The patient will be asked to avoid certain foods prior to and during the 24-hour test, including chocolate, olives, bananas, pineapple and its juice, all tomato products, plums, eggplant, avocado, kiwi fruit, nuts, especially walnuts, tea, coffee and alcohol. They will also be asked to avoid certain medications two days prior to the test, including certain cough, cold and flu medicines; hypertension medications; muscle relaxants; Valium and Flexeril; and MAO inhibitors, including natural herbs purchased in health food stores that produce the same effect. This is because they contain substances that might artificially raise serotonin levels and give a false test result.

Endoscopy

In this test, a flexible camera, called an endoscope, is used to examine the digestive tract. The tube can be inserted down the back of the throat (gastroscopy) or via the rectum (colonoscopy). In both cases the patient will be offered sedation. If abnormal-looking tissues are found during this procedure, a sample can be collected and examined under a microscope. A tissue biopsy like this can be the only definitive test for a NET cancer.

Endoscopic Ultrasound

In this test, an ultrasound is first used to locate suspect areas, before the endoscopy is performed.

Wireless Capsule Endoscopy

This is a noninvasive procedure in which a small capsule containing a video camera is swallowed by the patient. As it passes through the gastrointestinal tract it records the mucosa of the small bowel. These images are transmitted by a radiofrequency signal to a data recorder attached to the patient’s waist. After approximately 8 hours the capsule is excreted and the recorded data is downloaded to a computer where it can be viewed, edited and recorded.

Scans to help diagnose NET cancers

There are also a number of scans the patient may be asked to have. The physician will request the specific test that he/she requires and this may change dependent on the stage of disease and reason for scanning.

There are different reasons for different scans to be used, these are:

  • screening
  • detecting the primary tumor in a patient suspected of a NET
  • assessing extent of disease
  • assessing response to treatment
  • follow up after an initial diagnosis and/or treatment

NB: There is no standard group of tests – each patient may need to undergo a different combination of tests. If you have any questions about these tests, please confer with your medical team.

OctreoScan®

This scan uses a body imaging technique. Cells that receive hormonal messages do so through receptors on the surface of the cells. For reasons that are not understood, many neuroendocrine tumor cells possess especially strong receptors; for example, GEP-NETs often have strong receptors for somatostatin, a very common hormone. The OctreoScan® uses a synthetic form of somatostatin, which is chemically bound to a radioactive substance. This is then injected via a vein in the arm and then observed 24 hours later using a radio-sensitive scan. These scans can diagnose and locate around 80-90% of GEP-NETs, although further scans, such as PET scans may still be required.

CT Scan

A CT (Computer Tomography) scanner is a special type of X-ray machine. A CT scan uses ionizing radiation to provide a three-dimensional picture of the inside of the body. It can be used to determine the position and size of tumors, and regular scans are useful to find out more about the rate of tumor growth and how the tumor is responding to treatment. Before the scan, the patient may have an injection or drink a fluid containing a dye that shows up on the scan.

MRI Scan

A Magnetic Resonance Imaging (MRI) scan can be used to locate a tumor. Magnetism is used instead of X-rays to produce soft-tissue images that can distinguish between normal and diseased tissue. If a tumor is identified in this way, further tests may be needed to confirm what type of tumor it is.

PET Scan

A Positive Emission Tomography (PET) scan is a nuclear medicine imaging technique which produces a three-dimensional image of functional processes in the body. When FDG-18 is injected into your body it travels to places where glucose is used for energy. It shows up cancers because they use glucose in a different way from normal tissue. And it will show up changes in tissues that use glucose as their main source of energy – for example, the brain. It is usually used in conjunction with a CT scan to build up a picture of the size, location and status of tumors.

PET scanners are very expensive and a limited number of hospitals have one. This means that a patient may have to travel to another hospital for their scan. Not everybody who has cancer will need to have a PET scan, other types of tests and scans may be more suitable.

MIBG Scan

An MIBG Scan is a nuclear medicine scan which involves an injection of a liquid radioactive material called iodine-123-meta-iodobenzylguanidine – MIBG for short. The radioactive material is injected into a vein on the front of your arm at the level of your elbow, or in the back of your hand.

A special gamma camera (a type of scanner), finds or confirms the presence of tumors. These tumors involve specific types of nerve tissues and most commonly include pheochromocytomas (a rare cancer of the adrenal gland which is located on the surface of the kidneys) and neuroblastomas (cancers which affect nerve tissue). Neuroblastoma tumors usually begin in the adrenal gland but may also be found elsewhere in the body.

Bone Scan

A bone scan looks for changes or abnormalities in the bones. It is also called a radionuclide scan, or a scintigram and is usually done in the medical physics department, nuclear medicine department, or X-ray department of the hospital.

A bone scan can look at a particular joint or bone. In cancer diagnosis, it is more usual to scan the whole body.

Echocardiogram

Carcinoid tumors release chemicals called serotonin and tachykinins into the blood stream which can travel to the heart and affect the cardiac valves. If you have been diagnosed with a midgut carcinoid your doctor may do a blood test called a NT proBNP. If the result of this test is elevated, then he/she will send you for an echocardiogram to examine your heart. This is an ultrasound of your heart and is usually performed by a cardiac technician.

A small amount of sterile water will be injected into a vein and this is pictured as it passes around the heart. Depending on the results you may need two further investigations:

  • Transesophageal echocardiogram
  • Cardiac catheterisation