Neuroblastoma is a complex cancer and a number of tests have to be carried out over one to two weeks to ascertain the type and size of the tumour. As this is a rare disease some samples of the tumour may be sent to specialist centres (such as in the United States where there are approx 500 cases of Neuroblastoma a year). This may require waiting sometimes up to 2 weeks to get all the results. Although the wait may be agonizing, the exact assessment of the disease before beginning treatment is very important as the results obtained can affect the type and length of treatment.
A small piece of tumour is often taken for examination. This test is known as a biopsy. It involves an operation with a general anaesthetic and a piece of tumour is taken out through a small cut (incision) in the skin. Alternatively, a piece of tumour may be drawn up through a needle (needle biopsy).
Blood for testing may be taken from a vein in your child’s arm or by a finger prick.
A simple special test in the diagnosis of neuroblastoma measures something called the Vanillyl Mandelic Acid. This test may also be referred to as either the ‘VMA’ or the “urine catecholamine’ test. VMA is a chemical found in the urine, often in raised levels when a child has neuroblastoma and this can be a useful indicator.
Ordinary X-rays, Ultra sound tests and special scans give confirmation of the presence of the main neuroblastoma (referred to as the “primary site’) and also to show if there are any other tumour cells which have spread to other parts of the child’s body (“secondary tumours” or “mestastases”);
a) X rays may be taken
b) CT scan – the CT scanner (CT standing for Computerised Tomography) takes multiple x-ray films and these are converted by a computer into a kind of 3D view of either the whole or part of the body.
c) Ultrasound scan – the ultrasound scan will be a familiar procedure to all mothers who had this performed during pregnancy. It works by passing a “sonar” (like a small microphone) over the surface of the child’s body. The sound waves produced by the sonar “bounce” from the solid organs inside the body and are recorded on the screen. The Radiologist and Oncologist can see the outlines or shadow of normal organs and of any tumour or abnormality inside the body.
d) mIBG scan – mIBG stands for “meta-iodobenzylguanidine”. This substance is usually taken up by the neuroblastoma cells. Mibg contains radioactive material (not in a dangerous quantity but precaution needs to be taken handling nappies for a brief period) and this is administered by injection into the blood stream. When mIBG accumulates in the neuroblastoma cells, the radioactive material can de detected by means of a special type of x-ray machine called a gamma camera scanner. This type of scan is obviously a very useful diagnostic tool, giving a complete picture of the whereabouts of tumour cells in the body. There are however exceptions when some tumours for some unknown reason do not take up the mIBG (mIBG negative).
e) Bone scan – A bone scan involves an injection of a small amount of radioactive dye (not in a dangerous quantity) into a vein, usually in the hand or forearm. This radioactive material gathers in bones where the tumour has spread and these can be seen when pictures are taken on a gamma camera. Some hospitals may use a mIBG scan as a way of obtaining the same information as that obtained by the bone scan.
f) NMR/MRI – this test is referred to by either the initials NMR (Nuclear Magnetic Resonance) or MRI (Magnetic Resonance Imaging). The scan relies on magnetism and thus radiation is not used. It takes longer than a CT scan and is quite noisy. There are no known side effect to this type of scan.
g) Apart from the need for an injection of “contrast” during some CT scans and the injection for a bone scan or mIBG scan, none of the above investigations are painful. Some of the scans require that the child remains still for quite some time and to assist sedation may be given or a general anaesthetic may be needed for some children (particularly babies and toddlers) to have the test.
The most common sites to which neuroblastoma cells spread are bones and the bone marrow. To detect tumour cells in the bone, a bone scan or a mIBG scan will be carried out – or both.
To examine the bone marrow for tumour cells, a needle is inserted into one of the larger bones (usually the hip bone) and a small quantity of bone marrow, found at the centre of the bone is drawn out. This is called an “aspirate”. A “trephine” involves taking a very small piece of the bone at the site where the bone marrow is drawn out. To make sure that the test is as accurate as possible, aspirates and trephines may be taken from more than one site; usually from the hip bones on either side of the body. The child will always be given a general anaesthetic before these tests and will be slightly sore after the tests so may need some light pain relief.
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