PRRT Peptide Receptor Radionuclide Therapy

PRRT is a therapy to treat neuroendocrine tumors that has been used for several years (possibly a decade) in Europe. It uses radioactive elements attached to Octreotide to shrink the tumors. This treatment works because most neuroendocrine tumors have receptors that bind the naturally occurring chemical somatostatin. Octreotide is simply a synthetic version of somatostatin, so Octreotide goes straight to NETs just like somatostatin would.

Somatostatin is a naturally calming compound. When it goes to the cell membrane of a carcinoid cell, it attaches to its receptors on the cell membrane. Then it makes the cell slow down and not produce so much of the neurotransmittors, peptides, or hormones that the tumor usually makes. Therefore, somatostatin is part of a feedback mechanism that tells cells that their secretions are not necessary, so the cells decrease making the secretions that incidentally make carcinoid patients sick.
Since it is a somatostatin analog, Octreotide goes naturally to carcinoid cells, and when a radionuclide is attached to Octreotide then the radiation affects the carcinoid tumor. There are three different radionuclides that have been used in PRRT: Indium-111, Yttrium-90, and Lutetium-177. One of the reasons to use one of the radionuclides versus another is that they have different ranges of penetration.

The doctors use the radionuclide that will penetrate the tumor, but not destroy normal tissue that is around the tumor. Indium-111 has the shortest range of penetration; Lutetium-177 has a range of 2mm; and Yttrium-90 has a range of 12mm. There is more information about PRRT on the Caring for Carcinoid Foundation website at www.caringforcarcinoid.org/PRRT.


The use of Gallium-68 DOTATE PET/CT and PRRT is so new that scientists just had their first conference June 23-26, 2011 at Bad Berka, Germany. Patients are considered for PRRT if their scans show an inoperable tumor(s) that can be measured on the scans, or if their symptoms are not well managed by Sandostatin or Octreotide therapy. This website contains information for patients who want to have PRRT at Bad Berka, Germany: http://www.prrtinfo.org/.

PRRT requires a series of treatments. Reading the accounts of patients (on Cancer Compass) who went to Rotterdam for PRRT reported that they would go for one week at a time, and stay at a local hotel. The treatment would take place at a medical center to which they returned several days in a row. The patients would have to stay over the weekend to make sure they were well enough to travel, then fly home on Monday. A couple years ago people were writing that they would return home for a couple months before returning for treatments two through four. Results were usually very good, with tumors shrinking and symptoms being reduced.

However, I have learned this year that PRRT can have side effects that include leukemia and bone marrow toxicity. The leukemia was written as an effect that can show up later in life, but a woman suffering from bone marrow toxicity had it happen immediately after her PRRT treatment. Her bone marrow was not making the proper amount of platelets and red blood cells, but she was being treated for the condition and was recovering. This just reminds us that every treatment has side effects, so we need to know what they are and how to fight them.

There isn't much data in the USA, yet, on PRRT. However, this weekend (11-11-11) there is a conference at MD Anderson Medical Center in Houston, Texas, under the leadership of a Dr. Lao, about the progress they have made on doing PRRT in this country. Possibly, next week I can report on a date for PRRT to be available to us without a flight across the ocean.

Update: Well, there is no date for PRRT in the US. There are still hoops for the doctors and universities to jump through before the therapy is available in the USA. If you would like to see a synopsis of what happened at the conference at MD Anderson Medical Center, see this blog www.lucysnoidblog.blogspot.com . Lucy was at the conference and she has a great account of how PRRT works and why it is not available here.

Praying for the best possible result,
Sharon