Diagnosing phaeochromocytomas
You have tests to diagnose phaeochromocytomas. These include blood and urine tests, CT, MRI and PET scans, and an MIBG scan. Test results can show your cancer type and whether it has spread.
Symptoms of phaeochromocytomas
Diagnosing phaeochromocytomas can be difficult. This is because they can cause a range of symptoms. And many of these can be caused by other conditions that are much more common.
Blood and urine tests
Your doctor will ask you to have a plasma metanephrine test. This measures the amount of metanephrines in your urine (pee) and sometimes your blood (plasma). The body makes metanephrines when it breaks down the hormones adrenaline and noradrenaline.
Phaeochromocytomas can make large amounts of these hormones. This means the level of metanephrines in your blood and urine are higher than normal. You collect your urine over 24 hours to give a more accurate result. Your doctor will tell you how to do this.
They will tell you what you should avoid before having these tests. This includes:
- coffee
- tea
- cola
- nicotine or smoke
- paracetamol
- exercise
This is because they can affect your test results. Your doctor will also tell you if there are any medicines that you need to stop taking before and during the tests.
For the blood test, your doctor or nurse will usually ask you to lie down for 30 minutes before they take the sample.
Scans
Scans can show where a tumour is, how big it is and whether it has spread.
The tests you might have include:
- CT scan
- MRI scan
- MIBG scan
- DOTATATE PET scan
- FDG PET scan
CT scan
CT (or CAT) scan stands for computed (axial) tomography. It uses x-rays and a computer to create detailed pictures of the inside of your body.
You usually have a CT scan of your chest and tummy (abdomen).
MRI scan
MRI stands for magnetic resonance imaging. It uses magnetism and radio waves to take pictures of the inside of the body. It usually takes between 15 and 90 minutes.
mIBG scan
This is a specialised scan that doctors might use to diagnose phaeochromocytoma. They can also see if it has spread to other parts of your body. You have the scan in the nuclear medicine department at the hospital.
First, you have an injection of a small amount of a radioactive chemical called mIBG (meta-iodo-benzyl-guanidine). You have your scan 4 hours later. The phaeochromocytoma cells take up the mIBG, which then show up on the scan. You may have to go back to the hospital the next day to have another scan.
After you have had the radioactive injection, you need to drink plenty and go to the toilet regularly. This is to help flush out the excess mIBG and make the images on the scan clearer.
After the injection and for the rest of the day, you should avoid long periods of close contact with pregnant women and children.
The team at your hospital will give you advice about this.
DOTATATE PET scan
In some hospitals, instead of an mIBG scan, you may have a DOTATATE PET scan. This helps to diagnose phaeochromocytoma and to see if it has spread. With this type of scan you have a radioactive drug called 68-Ga-DOTATATE. This drug binds to certain receptors on tumour cells and shows up on the scan.
You have the 68-Ga-DOTATATE as an injection into a vein in your arm. You then wait 60 to 90 minutes before having a PET scan or PET-CT scan.
For the rest of the day after having the radioactive injection, you should avoid long periods of close contact with children and pregnant women. The team in the nuclear medicine department will give you advice about this.
FDG PET scan
This is the most common type of PET scan. The doctors use a different radioactive drug (tracer) called fluorodeoxyglucose (FDG). You might have this type of PET scan before your operation to remove the tumour.
Staging phaechromocytomas
Doctors have a new staging system for phaechromocytomas. But this is still not widely used. The standard way to stage phaechromocytomas is to say if it has:
- spread around the body - this is metastatic phaechromocytoma
- not spread - this is nonmetastatic phaechromocytoma
