[68Ga]Ga-PSMA-11 PET imaging as a predictor for absorbed doses in organs at risk and small lesions in [177Lu]Lu-PSMA-617 treatment

• Published in: European journal of nuclear medicine and molecular imaging 2022-03, Vol.49 (4), p.1101-1112
• Main Authors: Peters, Steffie M. B., Hofferber, Regina, Privé, Bastiaan M., de Bakker, Maarten, Gotthardt, Martin, Janssen, Marcel, de Lange, Frank, Muselaers, Constantijn H. J., Mehra, Niven, Witjes, J. Alfred, Costa, Pedro F., Nagarajah, James, Konijnenberg, Mark W., Jentzen, Walter
• Format: Article
• Language: English
• Subjects: Antigens; Cancer therapies; Cardiology; Computed tomography; Correlation coefficients; Dipeptides; Dosimetry; Drug dosages; Exocrine glands; Gallium Radioisotopes; Heterocyclic Compounds, 1-Ring; Humans; Imaging; Internet resources; Kidneys; Lesions; Liver; Lutetium; Lutetium isotopes; Male; Medicine; Medicine & Public Health; Nuclear Medicine; Oncology; Organs; Organs at Risk - pathology; Original; Original Article; Orthopedics; Patients; Positron emission; Positron Emission Tomography Computed Tomography - methods; Positron-Emission Tomography; Prostate cancer; Prostate-Specific Antigen; Prostatic Neoplasms, Castration-Resistant - pathology; Radiation; Radiology; Radiopharmaceuticals - therapeutic use; Response rates; Salivary gland; Salivary glands; Scaling factors; Single photon emission computed tomography; Therapy; Tomography
• ISSN: 1619-7070; 1619-7089
• DOI: 10.1007/s00259-021-05538-2

Introduction Patient eligibility for [ 177 Lu]Lu-PSMA therapy remains a challenge, with only 40–60% response rate when patient selection is done based on the lesion uptake (SUV) on [ 68 Ga]Ga-PSMA-PET/CT. Prediction of absorbed dose based on this pre-treatment scan could improve patient selection and help to individualize treatment by maximizing the absorbed dose to target lesions while adhering to the threshold doses for the organs at risk (kidneys, salivary glands, and liver). Methods Ten patients with low-volume hormone-sensitive prostate cancer received a pre-therapeutic [ 68 Ga]Ga-PSMA-11 PET/CT, followed by 3 GBq [ 177 Lu]Lu-PSMA-617 therapy. Intra-therapeutically, SPECT/CT was acquired at 1, 24, 48, 72, and 168 h. Absorbed dose in organs and lesions ( n  = 22) was determined according to the MIRD scheme. Absorbed dose prediction based on [ 68 Ga]Ga-PSMA-PET/CT was performed using tracer uptake at 1 h post-injection and the mean tissue effective half-life on SPECT. Predicted PET/actual SPECT absorbed dose ratios were determined for each target volume. Results PET/SPECT absorbed dose ratio was 1.01 ± 0.21, 1.10 ± 0.15, 1.20 ± 0.34, and 1.11 ± 0.29 for kidneys (using a 2.2 scaling factor), liver, submandibular, and parotid glands, respectively. While a large inter-patient variation in lesion kinetics was observed, PET/SPECT absorbed dose ratio was 1.3 ± 0.7 (range: 0.4–2.7, correlation coefficient  r  = 0.69, p