The First Theranostic Conference at the American University of Beirut Medical Center.

amount of 177Lu for every cycle? Although this is now the standard approach, it is reasonable to ask whether advantages might accrue to administering different amounts of radioactivity at different treatment cycles. Kulkarni et al. from the Zentralklinik Bad Berka (Germany) reported on “Serial dosimetry during 177Lu-PSMA radioligand therapy in the same patient” [316]. The authors performed dosimetry, imaging, and other analyses at each cycle of therapy (Fig. 11). All dosimetric parameters pertaining to metastases showed a reduction between the first and second therapy cycles: uptake declined by 57%, residence time by 62%, and dose by 64%. In contrast, the renal uptake increased by 62% and the residence time was 34% higher at the second cycle. The mean renal dose was therefore higher in the following cycles (34%). The authors emphasized the importance of performing individual dosimetry at the first and at least the second cycle. These results require further study to understand the mechanisms at work but also suggest that we may want to adjust the amount of 177Lu administered from cycle to cycle. This highlights lecture will be continued in the February issue of Newsline.