PRRT for neuroendocrine tumours

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For most essential points to best prepare for the procedure, please download the patient information brochure (PDF).
For a more elaborate explanation of the procedure and related points, please continue to read ahead.

Brief introduction

Principle

Peptide receptor radionuclide therapy (PRRT) involves administration of a radioactive particulate emitter (lutetium-177) linked to a ligand of somatostatin receptor (DOTATATE) in an attempt to selectively kill neuroendocrine carcinoma cells.

For a brief introduction of neuroendocrine tumours (NETs), neuroendocrine carcinomas (NECs) and somatostatin receptors (SSTR), please visit the page on SSTR PET.

The beta emitter lutetium-177 (or ¹⁷⁷Lu) complexed with DOTATATE is used as the radiopharmaceutical (RP) at SSNI for PRRT. It has a physical half-life of 162 h. Apart from beta particles, it also emits gamma photons that allow for its imaging (performing scan) following administration of PRRT.

It is mandatory for patients to undergo SSTR PET to determine suitability for PRRT. PRRT is best suited for those with well-differentiated and moderately differentiated NECs. Those with poorly differentiated NECs tend to show high FDG uptake, and hence, some of the PRRT candidates may have to also undergo a whole-body FDG PET-CT.

Lutetium-177 is avidly reabsorbed by kidney cells, hence, steps are taken to reduce radiation dose to the kidneys (including lowering the amount of drug administered), and in some cases, rejecting patients with severely impaired kidney function.

Likewise, particular caution is exercised in those with history and/or tendency of bone marrow suppression because of recent chemotherapy and/or extensive radiotherapy.

Indications (conditions in which advised)

Treatment of patients with NET expressing SSTR that are considered inoperable.
Treatment of patients with NET expressing SSTR with proved metastasis.

Considerations / steps before procedure

Written advice for PRRT by a medical doctor is a must for consideration of therapy. This doctor must be the same with who the patient could follow up for long term following PRRT.
SSTR PET-CT scan must have been carried out within 2 months before planned PRRT.
Prior appointment is a must. Availability of lutetium-177 is highly regulated, and order for it needs to be placed several days to weeks prior to the planned PRRT.
Patient must not be pregnant.
Patient must not be actively breastfeeding. If the patient was previously breastfeeding, it must be stopped at least 4 weeks prior to planned RAI therapy.
Short-acting forms of octreotide must be stopped at least 24 hours before the appointment in consultation with your referring doctor. Long-acting forms of octreotide or lanreotide should be preferably stopped for 3 to 4 weeks before the scheduled procedure.
Other medications (apart from those mentioned above) must not be stopped, and must be continued as advised by your doctor.
Wear loose-fitting but warm clothes.
Do not bring expensive jewellery or accessories along with you for the scan.
Proof of doctor's request is necessary for starting the procedure.
Food.
- 4 hours' fasting is needed. Avoid much longer durations of fasting.
- Avoid any food item that is likely to induce heart burn or nausea (e.g., excessively spicy or oily food).
The patient must be accompanied by a responsible carer.

What to expect as part of procedure?

Important steps

Patient registration and consent.
Handing over medical documents to the staff.
Patient preparation (change of dress, IV cannula insertion, explanation of procedure, etc.).
Pre-medications are injected in preparation for amino acid infusion.
Amino acid infusion is started 30 min after injection of pre-medications. (This is done to reduce the absorption of RP by kidney cells).
After 30 min of starting amino acid infusion, RP is injected slowly over 20 min.
Amino acid infusion is continued for further 4 hours.
Patient's heart rate and blood pressure would be recorded a few times during the infusion.
Patient is released for the day.
Next day: Post-therapy scan is performed, which could take ~1 hour. A dose of octreotide might be administered (in consultation with your main treating doctor).
Expect discharge summary to be issued within 4 hours of scan completion.

Discomfort / risks during procedure

Pain during IV cannula insertion.
There is small risk of flare up of symptoms that were experienced before PRRT few minutes to hours after starting RP infusion.
Amino acids can cause nausea and/or vomiting.
Amino acids could be recognized as 'foreign substance', and hence there is risk of very severe allergic reactions. However, corticosteroids are administered before amino acid infusion, which reduce the likelihood of the same.

Time taken for the entire patient visit

Day 1: 6 - 7 hours.
Day 2: 2 hours.

What to expect after procedure?

Precautions / special care

Maintain at least 1 metre distance from pregnant ladies and young children below 10 years' age (10 days).
Avoid sharing bed with adults (6 days).
Avoid sharing bed with pregnant ladies and young children (18 days).
10 days: have at least 3 litres water everyday. Do not hold urine, and try to pass urine as many times as possible.
Flush twice after using the washroom (10 days).
Avoid eating from the same plate and spoons as others without washing (10 days).
Clothes and utensils need not be washed separately.
Patient must avoid cooking food for others (10 days).
There is no need to use discardable plates and spoons.
Female patients must avoid pregnancy (at least 6 months).
Male patients must avoid fathering a child (at least 3 months).

Discomfort / risks

There is small risk of flare up of symptoms that were experienced before PRRT few minutes to hours after starting RP infusion.
There is a small risk of bone marrow suppression (with possibly increased risk of infections, anaemia and low platelets). However, you will monitored for the same, and you are expected to be in touch with your main treating doctor.

Time taken for summary generation

4 hours following post-therapy scan completion.

Additional reading

For additional information, please visit the following links.

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