Peptide receptor radionuclide therapy (PRRT)

PRRT is a type of internal radiotherapy. You might have it as a treatment for a neuroendocrine tumour (NET) that can’t be removed or that has spread to other parts of the body and is causing symptoms.

What is internal radiotherapy?

Internal radiotherapy means giving radiotherapy to the cancer from inside the body. The treatment gives a high dose of radiation to the cancer, but little to the surrounding tissues. 

There are different types of internal radiotherapy. For NETs, you might have:

• peptide receptor radionuclide therapy (PRRT)
• radioactive iodine MIBG (131 I-MIBG)

How PRRT works

Some neuroendocrine cells have proteins (receptors) on the outside of them called somatostatin receptors. The hormone somatostatin attaches to these receptors and causes changes in the cell. For example, they may tell the cell to slow down the production of hormones. 

Special scans such as PET scans or octreotide scans can check whether the NET has these receptors. If the NET has somatostatin receptors, doctors can use them to target radiotherapy. 

In the laboratory, doctors attach a radioactive substance to a man made form of the hormone somatostatin (a somatostatin analogue). This radioactive treatment circulates through your body in the bloodstream and attaches to the somatostatin receptors on the NET cells. It then enters the cell and kills it from the inside.

Doctors usually use a treatment called lutetium oxodotreotide (Lutathera).

When do I have PRRT?

You might have PRRT if you have a NET that can’t be completely removed by surgery or that has spread to other parts of the body. Your NET must have started in the pancreas or the gut (the gastrointestinal tract). The gut includes the:

• food pipe (oesophagus)
• stomach
• bowel
• rectum (back passage)

Before the start of treatment, your doctor also checks that the NET has somatostatin receptors on its surface. You usually have a radioactive scan such as octreotide or gallium dotatate PET scan to check for this.

How you have PRRT

Before

You see a doctor and have blood tests and a physical examination. If you are taking octreotide or lanreotide injections every day, your doctor might ask you to stop it for 12 hours before the treatment. If you are having octreotide or lanreotide injections every month, your doctor might ask you to stop them a month before the treatment.  

Your doctor or specialist nurse will tell you which drugs you need to stop before the treatment.

Having PRRT

You usually have treatment in the nuclear medicine department. It can take around 5 hours. 

A nurse or radiographer puts a small tube (cannula) into your arm or back of your hand. They then attach a drip of amino acids to the cannula. Amino acids are the building blocks of proteins. It helps to protect the kidneys from the radioactive treatment.

You have the drip of amino acids for one hour and then you start the radioactive drip. It takes about 30 minutes to have it. 

After the radioactive drip, you continue to have the amino acids infusion for another 3 hours.

You usually have PRRT every 2 to 3 months. You have up to 4 doses of treatment.

After PRRT

After PRRT, you will be slightly radioactive. So you might need to stay in hospital for 1 or 2 days to make sure the radioactivity drops to a safe level before you go home. In some hospitals, you may be able to go home later the same day if you are feeling well.  

You usually have special scans to check how much radiation is left in your body.

After you go home, there are still some safety precautions that you need to follow. Your doctor or specialist nurse will tell you about them and how long you need to do them for. The precautions might include:

• avoiding close contact, such as hugging with young children and pregnant women
• double flushing the toilet
• sleeping in a separate bed to your partner

Side effects

PRRT can cause side effects. These include:

A drop in the number of blood cells

You might have a drop in the number of blood cells such as red blood cells, white blood cells and platelets. This can increase your risk of breathlessness, infection and bleeding.

Feeling or being sick

This is usually caused by the amino acids drip. You have anti sickness medicine before the start of treatment to help with this.

Inflammation of the kidneys

This can happen because your body gets rid of the radiation through the kidneys. You have a drip of amino acids before and after the treatment to protect the kidneys from the effect of the radiation.

Pain

Pain can be caused by swelling (oedema) around the NET. Tell your doctor or nurse if you have this, they can give you medicines such as painkillers and steroids to help.

Follow up

After you finish treatment, you have regular blood tests to check how well your kidneys are working and the levels of blood cells in your body.

You usually have blood tests every week or every 2 weeks for the first 2 months. You then have blood tests less often. You may have them at the hospital or at your GP surgery.

Coping

Treatment for neuroendocrine tumours can be difficult to cope with for some people. Your nurse will give you phone numbers to call if you have any problems at home.