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.
This type of molecular radiation therapy can only be conducted on patients who have somatostatin receptor-positive tumors. Many, but not all, forms of neuroendocrine tumors express one or more somatostatin receptor subtypes. This means that when particular types of somatostatin analog drugs (most commonly octreotide) are brought in contact with the tumors, the receptors absorb the drug. When the drug (a small peptide of 8 aminoacids) is chemically bound to a form of radiation (the radionuclide), then the tumor absorbs both the chemical and the radiation. The emitted beta particles will then kill the tumors. The most effective radionuclides used at present are Lutetium-177 and Yttrium-90.
This makes PRRT a molecular targeted type of therapy, affecting those tumors with strong absorption of the radiation-laced peptide and affecting less or not, other tissue in the body. Precautions are taken prior to and during treatment to protect the kidneys from radiation damage since they are key to ridding the body of the administered radiation.