Background: Lu-177-radiopharmaceuticals can contain the metastable impurity [Lu-177m]lutetium with a physical half-life of 160.4 days, in varying concentrations depending on the route of production of the radionuclidic precursor [Lu-177]lutetium. Due to the long half-life of [Lu-177m]lutetium, difficulties with waste disposal or sterility testing could arise. Here, we analyzed several Lu-177-samples of different origins and suppliers regarding their Lu-177m-concentration.Results: All samples tested showed a Lu-177m-concentration in the range that was stated on the certificate of analysis from the supplier which is in accordance with the European Pharmacopoeia.Conclusions: Although all Lu-177m-concentrations were in accordance with the European Pharmacopoeia, we need to take into account the respective national legislation regarding radioactivity release limits. With regard to the German legislation, several probes for sterility testing in external laboratories could not be released for transport due to the concentration of [Lu-177m]lutetium. Moreover, waste water tanks should specifically be monitored for Lu-177m-concentration, when e.g. Lutathera (R) is administered in the clinic.
