The Impact of Metastable Lutetium-177 on a Nuclear Medicine Department

Objectives: In the United States, Lutetium-177 is being used to treat patient’s with gastro-entero-pancreatic neuroendocrine tumors with the FDA approved radiopharmaceutical Lutathera, which is manufactured by Advanced Accelerator Applications. In addition, Radiomedix, is manufacturing Lutetium-177-PSMA to treat patients with metastatic prostate cancer as part of a phase III clinical trial which is run by Endocyte. Each company uses a different process to manufacture the Lutetium, one of which adds a small amount of metastable Lutetium-177 which has a 160.4 day half-life. Without the metastable component, Lutetium-177 has a 6.65 day half-life. The difference in manufacturing methods may lead to differences in handling and disposing of the radioactive material. The purpose here is to share a single institution’s experience, OHSU, with Lutetium-177 from different manufacturers.

Methods: After administration of the radionuclide therapy, any radioactive waste is stored in a secure area to decay in storage. With a half-life of 6.65 days, our process is to check for any residual activity at approximately 65 days or 10 half-lives. After this decay period, we compared residual activity in multiple vials between manufacturer’s which had the same calibration date or were within one or two days of each other. To do this comparison, we measured the vial in a dose calibrator and also withdrew 1cc from each vial and measured the counts per minute in a Perkin Elmer Wizard well counter.

Results: When comparing waste from each manufacturer which had the same calibration date or were within one or two days of each other, we noticed that measured counts per minute from the well counter were 200% higher for vials from AAA. This phenomenon is consistent across all vials that were compared. We believe this is directly correlated to the metastable component that can be found in Lutetium-177 from AAA. The prolonged presence of radioactivity in the vials from AAA have required us to use a third-party company for disposal of this radioactive waste, which has led to increase in space needed for decay in storage and an additional operating cost to properly handle this material. Conclusion: In summary, Lutetium-177 has become a vital tool for radionuclide therapy, however, there are important considerations for decay and disposal of the radioactive waste which will vary based on the method of production. Having this information available when starting new programs and service lines is critical to long term success and compliance with regulatory agencies.