Peptide Receptor Radionuclide Therapy (PRRT) is a form of molecular targeted therapy which is performed by using a small peptide (a somatostatin analog similar to octreotide) that is coupled with a radionuclide emitting beta radiation. PRRT is a novel nuclear medicine therapy (the first patients were treated in 1996) for the systemic treatment of metastasized neuroendocrine tumors. These types of tumors include gastroenteropancreatic tumors (socalled GEP-NETs), e.g. arising from the small bowel (often called carcinoid tumors), the pancreas, duodenum or stomach, but also from the large bowel or the lung and many other tissues (socalled diffuse neuroendocrine system). On this website these tumors are referred to as neuroendocrine tumors or NETs. A handful of medical centers in Europe have been doing PRRT since the mid-1990s (including Basel, Milano, Rotterdam, and Bad Berka). These few centers now have 15 years experience administering PRRT. A clinical trial has begun in the US on PRRT with Lutetium-177 DOTATATE in 2013.
Perhaps the simplest way to explain the workings of PRRT is to think about the analogy of a magnet and its ability to attract iron shavings. Think of a neuroendocrine tumor with somatostatin positive receptors as the magnet and the iron shavings are a somatatostatin analog chemical (Octreotide) to which is bound or attached to some radioactive material (the radionuclide Y90 or LU177). The receptors in the tumors attract the octreotide and this chemical with the radioactive material is absorbed into the tumor by the receptor. The radiation then starts to kill the tumor cells.
This makes PRRT a form of targeted therapy, able to impact those tumors that can absorb certain types of chemicals bound to radioactive materials. Since the
Typically most cancer patients want to understand the statistics associated with survival for their particular form of cancer. The survival rate and other measures in terms of months or years is almost always part of any report on the efficacy of a treatment. For patients being treated for a NET cancer there are several measures of treatment efficacy that are important when considering a treatment.
When you and your doctor are evaluating which treatment modality is right
The early efforts at PRRT were done with a form of Indium-111. This form of radiation was found to have a very short radius of action, causing little or no collateral damage to nearby tissue, but was most effective on very small tumors. Doctors using the Indium-111 found that it was not ideal for PRRT because the small particle range resulted in short tissue penetration and limited effectiveness on tumors 2cm and larger.
In the late 1990s and early 2000s, Doctors started using two other
What are the Risks?
As with most, if not all, of the treatment options open to neuroendocrine tumor patients, there are risks associated with using PRRT to treat metastasized tumors. The greatest risks arise from radiation toxicity affecting three things: 1) the blood system producing Red Blood Cells, White Blood Cells and Blood Platelets, 2) the functioning of the kidneys and 3) the functioning of the liver.
At one time kidney impairment or renal insufficiency was a significant risk, but as
Peptide Receptor Radionuclide Therapy (PRRT) will not work on all neuroendocrine tumors. For this treatment to work you MUST have somatostatin receptors in your tumors. When a somatostatin analog (like a form of octreotide) is combined with a radionuclide such as Lutetium-177 (LU177) or Yttrium-90 (Y90), it has a strong affinity for the somatostatin receptor subtype-2 that can exist in the NET tumor. This means that the radioactive material put in the body for the treatment will be absorbed
This is a partial list of centers that offer PRRT to patients from North America- Please feel free to contact us to add other centers to the list. As with any medical decision it is advisable to contact or interview more than one provider and understand the differences in approach between centers offering PRRT therapy.