Purpose: A strategy for management of radioactive waste associated with 177 Lu-dotatate (Lutathera ® ) treatments was established in our institution based on predicted storage times of 3 to 5 years extrapolated from the results of a 2-year measurement study. The aim of this work was to validate the model used by identifying contaminants and confirming disposal based on the clearance level twice-the-background was within expected time frames.
Methods: We conducted a prospective series of measurements of radioactive waste associated with the first 65 treatments administered. Sequential measurements of the first 45 vials used were performed on a dose calibrator to identify contaminants. Exposure rates in contact were monitored with a dose ratemeter on a 6-monthly basis for all types of waste stored: 46 empty vials, 19 vials partially used and 67 biohazard containers. Results: Initial median activity of the first vials used was 118 MBq (4 - 4188 MBq). For each vial, the decay curve of activity obtained was adjusted to a bi-exponential model. The major component, representing 99.7 % of activity, has a half-life of 6.5 ± 0.2 days, corresponding to 177 Lu. The second, representing only 0.3 % of the activity and having a half-life of 156 ± 24 days corresponding to 177m Lu, determines necessary storage times. Partially used vials can be disposed of after 5 years, other waste after 3 years. Compliance with the regulatory clearance level is achieved within expected time frames.
Conclusion: Although only present as traces, 177m Lu results in major radioactive waste disposal issues for hospitals. Availability of radiopharmaceuticals without impurities appears to be crucial for an expanding use of targeted radionuclide therapy.