Lacrimal Glands May Represent Organs at Risk for Radionuclide Therapy of Prostate Cancer with [(177)Lu]DKFZ-PSMA-617

PURPOSE - Calculating the absorbed dose is important for the determination of risk and therapeutic benefit of internal radiation therapy. The aim of this study was to perform image-based absorbed dose calculation for critical organs during the first cycle of [(177)Lu]DKFZ-PSMA-617 therapy in a small cohort of patients with metastatic prostate cancer.

PROCEDURES - Nine patients with a history of prostate cancer documented by histopathology and radiologic evidence of metastatic diseases underwent radioligand therapy with [(177)Lu]DKFZ-PSMA-617. Conjugated planar whole-body scintigraphies acquired at 0.5, 24, 48, 72, and 168 h post-injection were analyzed by regions of interest, and time-activity curves were generated for various organs. Cumulated activities and residence times were calculated by bi-exponential fit of the time-activity curves. Mean absorbed doses were finally estimated using OLINDA/EXM1.1™. Additionally, the uncertainty when omitting the last measurement (168 h p.i.) was studied.

RESULTS - The following mean absorbed doses were calculated: 2.82 mGy/MBq for the lacrimal glands, 0.72 mGy/MBq for the salivary glands, 0.53 mGy/MBq for the kidneys, and 0.42 mGy/MBq for the nasal mucous membrane. Omitting the last measurement resulted in a mean deviation of 10 to 25 % for absorbed dose values as compared to the ones received by analyzing all measurements.

COCLUSIONS - Absorbed organ doses of [(177)Lu]DKFZ-PSMA-617 therapy are not likely to be critical for kidneys, salivary glands, and the nasal mucous membrane. The lacrimal glands may represent the dose-limiting organs. Whole-body scintigraphy appears sufficient for dose estimation, but late measurements are mandatory, if accurate dose calculation is required.

Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging. 2016 Feb 26 [Epub ahead of print]

Melanie Hohberg, Wolfgang Eschner, Matthias Schmidt, Markus Dietlein, Carsten Kobe, Thomas Fischer, Alexander Drzezga, Markus Wild

Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany. Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany., Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany., Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany., Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany., Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany., Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany., Department of Nuclear Medicine, University Hospital of Cologne, Kerpener Str. 62, Cologne, 50937, Germany.

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