At UZ Leuven, peptide receptor radionuclide therapy (PRRT) is being applied for metastatic neurendocrine tumours. Everyone has neuroendocrine cells in their body. These cells produce hormones. But sometimes these cells start presenting unbridled growth - and form tumours. This can be linked to unwanted hormonal production. The ground-breaking PRRT treatment, which consists of injecting radioactive small proteins, is an option when metastatic cells can no longer be treated with surgery, chemotherapy or external radiation.
Radioactive lutetium
Apart from being rare - only 1 in a 100 tumours - neuroendocrine tumours are also difficult to treat. Prof. dr. Christophe Deroose, nuclear medicine expert at UZ Leuven: “Neuroendocrine tumours mostly occur in the gastrointestinal tract, the pancreas and the lungs. These areas are difficult to radiate from the outside, especially when it concerns metastasis. In which case it may be an option to radiate inside the body. The patients are injected with a radiopeptide: a molecular drug with a radioactive charge lutetium-177. The molecule binds itself to specific receptors on the outside of the cancer cells. When the radiopeptide binds to the the tumour cells, it delivers a targeted high dose of radiation. By injecting the molecular medicine in the bloodstream, cancer cells throughout the body can be radiated from the inside in one go.”
We are sometimes able to reduce the patients' chance of metastasis up to 80 per cent. For some patients, it makes cancer manageable for a number of years, which is a big step forwards.
Prof. dr. Christophe Deroose
PET-scan gauges chance of success
UZ Leuven is one of the worldwide pioneers to have grown PRRT treatment into a fully-fledged therapy. UZ Leuven experts are currently using the third generation of molecular medication with lutetium-177. The chance for success can be estimated in advance by screening the presence of the target, the somatostatin receptor, with a PET scan. The concept relies on the use of one building block, a basic molecule, that binds to a specific target on the cancer cells. The physicians first mark this basic molecule with the isotope gallium-68, after which they make PET scans of the spread of the cancer cells in te body. If there are sufficient receptors, the combine the basic molecule with lutetium-177, which then delivers the necessary radiation that can stop cancer cells.
Prof. dr. Deroose: “The treatment has few adverse effects, because radioactive molecules mainly bind to cancer cells, and hardly to healthy cells. We are sometimes able to reduce the patients' chance of metastasis with up to 80 per cent. For some patients it makes cancer manageable for several years, which is a big step forward. Unfortunatelty, a full recovery from metastatic cancer is very exceptional. It is possible that in future new forms of radioactive charge can make the effect even more powerful.”
Before therapy (left) this PET/CT-scan shows metastasis in and behind the liver (bright points) that absorbed the diagnostic agent to a very high degree. Post-therapy (right) with the medicine containing lutetium-177 the metastasis can no longer be detected.
Duo-molecules
The success of radionuclide therapy for the treatment of metastatic neuroendocrine tumours can be a stepping stone to apply molecular therapy to other types of cancer the coming years. Since 1 January 2022, the molecular drug used by UZ Leuven to treat metastatic neuroendocrine tumours, is reimbursed by the NIHDI.
The clinical development of the PRRT treatment at UZ Leuven is largely thanks to an intense collaboration within the Leuven Cancer Institute, a KU Leuven and UZ Leuven centre that encourages researchers, physicians and nurses to work together in a multidisciplinary manner in the battle against cancer. The PRRT treatment requires close collaboration with the department of nuclear medicine (physicians, radiopharmacists, radiation physicists, technologists), gastroenterologists, pulmonologists, oncologists, surgeons, radiologists and nurses.