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<h3>Background and Importance</h3> Lutetium-177 (177Lu) is used in radiopharmaceuticals such as Pluvicto (177Lu-PSMA) for the treatment of metastatic castration-resistant prostate cancer and Lutathera (177Lu-oxodotreotide) for inoperable or metastatic gastro-enteropancreatic neuroendocrine tumours. The received doses are calibrated for activity at a given moment, with a tolerance of +/- 10% but discrepancies between announced and measured activities have been repeatedly observed suggesting potential under-calibration. <h3>Aim and Objectives</h3> To evaluate calibration discrepancies in 177Lu radiopharmaceutical doses between laboratory-reported and measured values. <h3>Material and Methods</h3> We analysed doses of lutetium-based radiopharmaceuticals received by eight radiopharmacy between January and December 2024. For each vial, the measured activity (in MBq) was compared with the certificate reference activity. Parameters collected included date/time of calibration, date/time of measurement, day of delivery, date of production and production site. <h3>Results</h3> A total of 1 040 deliveries of 177Lu-PSMA (n=754) and 177Lu-oxodotreotide (n=286) during this period were analysed. 32.3% of the vials came from Spain and 67.7% from Italy. The overall mean deviation between measured and reference values was –7.2%. Taking into account dose calibrator uncertainty (3%), 21.7% of vials (n=226) were under-calibrated beyond the ±10% tolerance, while 73.8% exceeded a -5% deviation. Doses from Spain showed >10% deviation in 16.4% of cases, representing 24.3% of all non-compliant vials. Italian vials accounted for 75.7% of >10% deviations, corresponding to 24.3% of batches from this origin. The deviation observed also varied according to logistical factors. Vials delivered on Mondays showed a greater average deviation (–7.9%) compared with those received on Fridays (–6.5%). No significant difference was observed according to the time elapsed between production and delivery (range: –6.7% to –7.3%). <h3>Conclusion and Relevance</h3> Although most measured values remained within the ±10% tolerance required for clinical use, a significant proportion of 177Lu doses showed deviations greater than –5%, raising concerns about systematic under-calibration. Both the origin of vials and delivery schedules appeared to impact these discrepancies, with higher deviations for Italian batches and Monday deliveries. These findings highlight the need for improved harmonisation of calibration procedures, currently under discussion at the European level, to ensure consistent and reliable dosing in 177Lu radiopharmaceutical therapies. <h3>Conflict of Interest</h3> No conflict of interest