Study Establishes Effective PRRT Dose

A neuroendocrine tumor (NET) is a type of tumor that originates in endocrine or nerve cells. These cells are found in many organs in the body, including the intestines, lungs, and pancreas. Some NETs are cancerous tumors that require treatment. Since they can originate in hormone-producing cells, NETs can cause a variety of symptoms triggered by hormone fluctuations.

Non-functional tumors do not produce hormones; they account for 60 percent of NETs. NETs that do produce hormones are categorized as functional. Their hormonal activity causes strong symptoms, making them easier to diagnose. For example, functional NETs can result in carcinoid syndrome; such cases experience symptoms like glucose blood level fluctuation and anxiety, which are triggered by hormone release.

Classification of NETs is based on size, location, spread, and microscopic appearance. The size of the tumor, its location, and its degree of spread in the body determine its stage.

Early-stage NETs are typically small and limited to a single organ or layer, while later stages indicate more extensive spread to neighboring lymph nodes and other organs. Pathologists examine tumors under the microscope to ascertain the exact type of NET. During microscopic examination of NET specimens, pathologists classify tumors according to degree of differentiation and proliferation rate.

Treatment regimens for NETs depend on tumor type and stage. In addition to traditional therapies such as chemotherapy and surgery, NETs can be treated with peptide receptor radionuclide therapy, or PRRT, which works by targeting somatostatin receptors on the tumor cell surface.

PRRT is suitable for somatostatin receptor-positive (SRP) tumors. If tumor cells do not express somatostatin receptors, the therapy will be ineffective against the tumor. Currently, the standard treatment for late-stage SRP NETs is PRRT with 177Lu-DOTATATE, a radioactive drug that binds to somatostatin receptors and enters tumor cells. Once inside the cells, the drug builds up and emits radiation that damages the tumor.

Chemical formulation and dosing play an important role in the effectiveness of PRRT. When administered alone, 177Lu-DOTATATE is usually eliminated from the patient’s body rapidly. A recent study published in the Journal of Nuclear Medicine aimed to maximize the therapeutic effect of the drug.

By modifying 177Lu-DOTATATE with a special dye called Evans blue, the researchers extended its availability in the body, therefore boosting its effect against tumor cells. The modified drug, now dubbed 177Lu-DOTA-EB-TATE, was the main focus of the study, which evaluated the effectiveness of different doses to identify the ideal dose for safe, effective NET treatment.

A total of 32 patients diagnosed with SRP NETs participated in the study. They were randomly assigned to three groups receiving different drug doses: 1.17, 1.89, and 3.97 GBq per cycle. Over the course of three cycles, all patient groups tolerated the modified drug well, with no significant side effects. The study findings demonstrated that 177Lu-DOTA-EB-TATE doses of 1.89 and 3.97 GBq per cycle were both effective in controlling NET tumors.

Based on the study findings, modified PRRT is a promising treatment modality. It demonstrates increased effectiveness against NETs and can significantly reduce mortality in late-stage NET patients.