Abstract
Purpose: PET-imaging with the prostate-specific membrane antigen-targeted radioligand 68Ga-PSMA-11 is regarded as a significant step forward in the diagnosis of prostate cancer (PCa). More recently, a PSMA-ligand was developed which can be labeled with 68Ga, 111In, 177Lu, and 90Y. This ligand, named PSMA-617, therefore enables both, diagnosis and therapy of PCa. The aim of this evaluation was to clinically investigate the distribution of 68Ga-PSMA-617 in normal tissues and in PCa lesions as well as to evaluate the radiation exposure by the radioligand in PET-imaging. Methods: Nineteen patients, most of them with recurrent PCa, were referred to 68Ga-PSMA-617-PET/CT. Quantitative assessment of tracer uptake of several organs and of 53 representative tumor lesions was performed in 15 patients at 1h and 3h post injection (p.i.). In four additional patients, the same procedure was conducted at 5min, 1h, 2h, 3h, 4h and 5h p.i. Based on the data of these four patients (mean injected dose of 231 MBq) the radiation exposure of a 68Ga-PSMA-617-PET/CT was identified. Results: Intense tracer uptake was observed in kidneys and salivary glands. In 14 of 19 patients (73.7%) at least one tumor suspicious lesion was detected at 3h p.i. Of 53 representative tumor lesions selected at 3h p.i., 47 lesions were visible at 1h p.i. Mean tumor-to-background ratio for SUVmax was 20.4 ± 17.3 (2.3 – 84.0) at 1h p.i. and 38.2 ± 38.6 (3.6 – 154.3) at 3h p.i. Average radiation exposure (effective dose) was approximately 0.021 mSv/MBq. Conclusion: Within healthy organs, kidneys and salivary glands showed the highest 68Ga-PSMA-617 uptake. The radiation exposure is relatively low. 68Ga-PSMA-617 shows PCa-lesions with very high contrast. Images conducted between 2-3h p.i. seem to be the best option with regard to radiotracer uptake and tumor contrast. Later images can help to clarify unclear lesions.
- Oncology: General
- Oncology: GU
- PET/CT
- PSMA
- Positron emission tomography
- Prostate cancer
- Prostate-specific membrane antigen
- dosimetry
- Copyright © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.