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Pretherapeutic 68Ga-PSMA-617 PET May Indicate the Dosimetry of 177Lu-PSMA-617 and 177Lu-EB-PSMA-617 in Main Organs and Tumor Lesions

Wang, Jingnan, MD*†; Zang, Jie, MD*†; Wang, Hao, MD*†; Liu, Qingxing, MD*†; Li, Fang, MD*†; Lin, Yansong, MD*†; Huo, Li, MD*†; Jacobson, Orit, MD; Niu, Gang, MD; Fan, Xinrong, MD§; Zhu, Zhaohui, MD*†; Chen, Xiaoyuan, MD

doi: 10.1097/RLU.0000000000002575
Original Articles
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Aim Combined 68Ga-PSMA-617 PET imaging and 177Lu-PSMA-617 therapy is a precise targeted theranostic approach for patients with metastatic castration-resistant prostate cancer (mCRPC). The purpose of this study was to determine whether pretherapeutic standard uptake value (SUV) in 68Ga-PSMA-617 PET could indicate the effective dose in the main organs and absorbed dose in tumor lesions.

Methods After institutional review board approval and informed consent, 9 patients with mCRPC were recruited and underwent 68Ga-PSMA-617 PET/CT scans. Five patients received 177Lu-PSMA-617 (1.30–1.42 GBq, 35–38.4 mCi) and then underwent serial whole-body planar imaging and SPECT/CT imaging of both thoracic and abdominal regions at 0.5-, 2-, 24-, 48-, and 72-hour time points. The other 4 patients received 177Lu-EB-PSMA-617 (0.80–1.1 GBq, 21.5–30 mCi) and then underwent the same imaging procedures at 2-, 24-, 72-, 120-, and 168-hour time points. The effective dose in the main organs and the absorbed dose in tumor lesions were calculated. Detailed correlations between the pretherapeutic SUV in 68Ga-PSMA-617 PET and effective dose in the main organs as well as absorbed dose in the tumor lesions were analyzed.

Results SUV of 68Ga-PSMA-617 PET was moderately correlated with effective dose in main organs (r = 0.610 for 177Lu-PSMA-617, r = 0.743 for 177Lu-EB-PSMA-617, both P < 0.001). SUV of tumor lesions in 68Ga-PSMA-617 PET had high correlation with those in 177Lu-PSMA-617 (r = 0.915, P < 0.001) and moderate correlation with those in 177Lu-EB-PSMA-617 (r = 0.611, P = 0.002).

Conclusions Pretherapeutic 68Ga-PSMA-617 PET may indicate the dosimetry of 177Lu-PSMA-617 and 177Lu-EB-PSMA-617. Both the effective dose in main organs and absorbed dose in tumor lesions correlate with SUV of 68Ga-PSMA-617 PET. This relationship may help select appropriate candidates for peptide receptor radionuclide therapy. Further investigations of larger cohorts are needed to confirm these initial findings.

From the *Department of Nuclear Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College Hospital, Beijing, China;

Beijing Key Laboratory of Molecular Targeted Diagnosis and Therapy in Nuclear Medicine, Beijing, China;

Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, MD; and

§Department of Urology, Chinese Academy of Medical Sciences and Peking Union Medical College Hospital, Beijing, China.

Received for publication November 26, 2018; revision accepted February 19, 2019.

Conflicts of interest and Sources of funding: This work is supported by the National Natural Science Foundation of China (81771874). This work is supported in part by the Key Project on Inter-Governmental International Scientific and Technological Innovation Cooperation in National Key Projects of Research and Development Plan (2016YFE0115400), the Intramural Research Program (IRP), National Institute of Biomedical Imaging and Bioengineering (NIBIB), and National Institutes of Health (NIH). This work is also partly supported by the Chinese Academy of Medical Science Major Collaborative Innovation Project (2016-I2M-1-011), Welfare Research Funding for Public Health Professionals (201402001), National Nature Science Foundation (81741142, 81871392), and Beijing Municipal Natural Science Foundation (7161012). None declared to all authors.

Correspondence to: Xinrong Fan, MD, Department of Urology, Chinese Academy of Medical Sciences and Peking Union Medical College Hospital, Wangfujing, Dongcheng District, Beijing 100730, People's Republic of China. E-mail: pumcfxr@126.com; Zhaohui Zhu, MD, Department of Nuclear Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College Hospital, Wangfujing, Dongcheng District, Beijing 100730, People's Republic of China. E-mail: 13611093752@163.com; Xiaoyuan Chen, MD, Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland, 20892, USA. E-mail: shawn.chen@nih.gov.

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