Patient dosimetry of 177Lu-PSMA I&T in metastatic prostate cancer treatment: the experience in Thailand

Kotchakorn Chatachot; Shuichi Shiratori; Tawatchai Chaiwatanarat; Kitiwat Khamwan

doi:10.1007/s12149-021-01659-8

Patient dosimetry of ¹⁷⁷Lu-PSMA I&T in metastatic prostate cancer treatment: the experience in Thailand

Ann Nucl Med. 2021 Nov;35(11):1193-1202. doi: 10.1007/s12149-021-01659-8. Epub 2021 Jul 26.

Authors

Kotchakorn Chatachot^{1

2

3}, Shuichi Shiratori^{4

5

3}, Tawatchai Chaiwatanarat^{4

3}, Kitiwat Khamwan^{6

7

8}

Affiliations

¹ Medical Physics Program, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
² Division of Nuclear Medicine, Department of Radiology, Buddhachinaraj Hospital, Phitsanulok, 65000, Thailand.
³ Chulalongkorn University Biomedical Imaging Group, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
⁴ Division of Nuclear Medicine, Department of Radiology, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, 10330, Thailand.
⁵ Division of Nuclear Medicine, Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.
⁶ Medical Physics Program, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand. kitiwat.k@chula.ac.th.
⁷ Division of Nuclear Medicine, Department of Radiology, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, 10330, Thailand. kitiwat.k@chula.ac.th.
⁸ Chulalongkorn University Biomedical Imaging Group, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand. kitiwat.k@chula.ac.th.

PMID: 34309816
DOI: 10.1007/s12149-021-01659-8

Abstract

Purpose: This study aimed to determine the radiation dosimetry for ¹⁷⁷Lu-PSMA imaging and therapy (I&T) in Thai patients who were treated for metastatic prostate cancer.

Methods: Whole-body planar images acquired at immediately, 4 and 24 h after ¹⁷⁷Lu-PSMA I&T injection (range 4.44-8.51 GBq) were collected from 12 treatment cycles of 8 prostate cancer patients. Region of interests (ROIs) were manually contoured on the whole-body, liver, spleen, urinary bladder, lacrimal glands, parotid, and submandibular glands to determine time-integrated activity (TIA) in source organs and fitted time-activity curves using mono-exponential extrapolation. The S values calculated utilizing non-uniform rational B-splines (NURBS) computational phantoms were extracted from the OLINDA/EXM v. 2.0 to calculate the absorbed dose coefficient in target organs according to the Medical Internal Radiation Dose (MIRD) scheme. The absorbed doses to bone marrow were estimated using the planar two-compartment image-based method by separating the high-uptake and low-uptake compartment. The spherical model was used to calculate the lacrimal gland absorbed doses.

Results: Mean absorbed dose coefficients to the kidneys, bone marrow, liver, urinary bladder, spleen, lacrimal glands, parotid, and submandibular glands were 0.81 ± 0.24, 0.02 ± 0.01, 0.13 ± 0.10, 0.27 ± 0.25, 0.16 ± 0.07, 3.62 ± 1.78, 0.21 ± 0.14, and 0.09 ± 0.07 Gy/GBq, respectively. Dose constraints for the kidneys (23 Gy) and bone marrow (2 Gy) were not reached in any patients. The absorbed dose in lacrimal glands calculated by the NURBS computational phantoms was slightly lower than the calculation based on the Cristy-Eckerman computational phantoms using OLINDA/EXM v. 1.0 by 6.37 ± 0.14%.

Conclusion: Dosimetry results in this study suggested that ¹⁷⁷Lu-PSMA I&T treatment with higher activities and more cycles is possible without the risk of damaging normal organs in prostate cancer patients.

Keywords: 177Lu-PSMA I&T; MIRD scheme; Radionuclide therapy; Theranostics.

MeSH terms

Humans
Male
Prostatic Neoplasms, Castration-Resistant*
Radiometry