Bone marrow dosimetry in low volume mHSPC patients receiving Lu-177-PSMA therapy using SPECT/CT

Dagmar Grob; Bastiaan M Privé; Constantijn H J Muselaers; Niven Mehra; James Nagarajah; Mark W Konijnenberg; Steffie M B Peters

doi:10.1186/s40658-024-00636-0

Bone marrow dosimetry in low volume mHSPC patients receiving Lu-177-PSMA therapy using SPECT/CT

EJNMMI Phys. 2024 Apr 3;11(1):34. doi: 10.1186/s40658-024-00636-0.

Authors

Dagmar Grob^{1

2}, Bastiaan M Privé^{1

3}, Constantijn H J Muselaers⁴, Niven Mehra⁵, James Nagarajah¹, Mark W Konijnenberg^{1

6}, Steffie M B Peters⁷

Affiliations

¹ Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
² Department of Healthcare and Information Technology, Slingeland Hospital, Doetinchem, The Netherlands.
³ Department of Radiation Oncology, Erasmus Medical Center, Rotterdam, The Netherlands.
⁴ Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands.
⁵ Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands.
⁶ Department of Radiology and Nuclear Medicine, Erasmus Medical Center, Rotterdam, The Netherlands.
⁷ Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands. steffie.peters@radboudumc.nl.

Abstract

Background: Bone marrow toxicity in advanced prostate cancer patients who receive [¹⁷⁷Lu]Lu-PSMA-617 is a well-known concern. In early stage patients; e.g. low volume metastatic hormone sensitive prostate cancer (mHSPC) patients, prevention of late bone marrow toxicity is even more crucial due to longer life expectancy. To date, bone marrow dosimetry is primarily performed using blood sampling. This method is time consuming and does not account for possible active bone marrow uptake. Therefore other methodologies are investigated. We calculated the bone marrow absorbed dose for [¹⁷⁷Lu]Lu-PSMA-617 in mHSPC patients using SPECT/CT imaging and compared it to the blood sampling method as reference.

Methods: Eight mHSPC patients underwent two cycles (3 and 6 GBq) of [¹⁷⁷Lu]Lu-PSMA-617 therapy. After each cycle, five time point (1 h, 1 day, 2 days, 3 days, 7 days) SPECT/CT was performed at kidney level. Bone marrow dosimetry was performed using commercial software by drawing ten 1.5 cm diameter spheres in the lowest ten vertebrae to determine the time-integrated activity. Simplified protocols using only 2 imaging time points and 3 vertebrae were also compared. Blood-based dosimetry was based on the blood sampling method according to the EANM guideline.

Results: Mean bone marrow absorbed dose was significantly different (p < 0.01) for the imaging based method (25.4 ± 8.7 mGy/GBq) and the blood based method (17.2 ± 3.4 mGy/GBq), with an increasing absorbed dose ratio between both methods over time. Bland Altman analysis of both simplification steps showed that differences in absorbed dose were all within the 95% limits of agreement.

Conclusion: This study showed that bone marrow absorbed dose after [¹⁷⁷Lu]Lu-PSMA-617 can be determined using an imaging-based method of the lower vertebrae, and simplified using 2 time points (1 and 7 days) and 3 vertebrae. An increasing absorbed dose ratio over time between the imaging-based method and blood-based method suggests that there might be specific bone marrow binding of [¹⁷⁷Lu]Lu-PSMA-617.

Keywords: 177-Lu-PSMA; Absorbed dose; Bone marrow dosimetry; Radionuclide therapy.