Peptide receptor radionuclide therapy (PRRT) for neuroendocrine tumours (NETs)

Peptide receptor radionuclide therapy (PRRT) is a type of radioisotope therapy. These treatments use radioactive medicines to treat some types of cancer. PRRT is also called:

• radioligand therapy
• molecular radiotherapy
• targeted radiotherapy
• radio labelled treatment
• targeted radionuclide therapy

PRRT is a possible treatment for some NETs that start in the pancreas or the digestive system . It is not a treatment for NECs.

What is radioisotope therapy?

Radioisotope therapy uses radioactive medicines to treat some cancer types. 

The radioisotope travels around your body in the bloodstream to the area where the cancer is. The radioactive part is called an isotope. It may be attached to another substance, which is designed to take the isotope to the cancer.

The cancer cells take up the radioisotope and get a high dose of radiation, which destroys them. The healthy cells receive a low dose or no radiation. 

There are different types of radioisotope therapy, including PRRT.

How PRRT works

Some neuroendocrine cells have proteins (receptors ) on the outside of them. These are 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 can check whether your NET has these receptors. If your NET has somatostatin receptors, doctors can use these receptors to target radioisotope therapy. 

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

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

When you might have PRRT

You might have PRRT if the surgeon can't completely remove your NET. Or if the NET has spread to other parts of your body.

You have special scans such as PET scans or octreotide scans . These can check whether your NET has somatostatin receptors. If it does, your doctors might offer you this treatment.

It is only a treatment for NETs that start in the pancreas or the gastrointestinal system. The gastrointestinal system includes the:

• food pipe (oesophagus)

• stomach

• bowel

• rectum (back passage)

How you have PRRT

Before

You see a doctor and have blood tests and a physical examination. Your doctor might ask you to stop octreotide or lanreotide injections. If you have these every day, you might stop them for 12 hours before the treatment. If you are have them every month, your doctor might ask you to stop 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 doctor puts a small tube (cannula) into your arm or back of your hand. They then attach a drip of amino acids to the cannula. This 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. This is 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. These 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 cancer 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.