Radiation dosimetry of [68Ga]PSMA-11 in low-risk prostate cancer patients

Kristina Sandgren; Lennart Johansson; Jan Axelsson; Joakim Jonsson; Mattias Ögren; Margareta Ögren; Martin Andersson; Sara Strandberg; Tufve Nyholm; Katrine Riklund; Anders Widmark

doi:10.1186/s40658-018-0239-2

Radiation dosimetry of [⁶⁸Ga]PSMA-11 in low-risk prostate cancer patients

EJNMMI Phys. 2019 Jan 11;6(1):2. doi: 10.1186/s40658-018-0239-2.

Affiliations

¹ Department of Radiation Sciences, Radiation Physics, Umeå University, 901 85, Umeå, Sweden. kristina.sandgren@umu.se.
² Department of Radiation Sciences, Radiation Physics, Umeå University, 901 85, Umeå, Sweden.
³ Department of Radiation Sciences, Diagnostic Radiology, Umeå University, Umeå, Sweden.
⁴ Department of Medical Radiation Physics, ITM, Lund University, Malmö, Sweden.

Abstract

Background: ⁶⁸Ga-labeled Glu-NH-CO-NH-Lys(Ahx)-HBED-CC ([⁶⁸Ga]PSMA-11) has been increasingly used to image prostate cancer using positron emission tomography (PET)/computed tomography (CT) both during diagnosis and treatment planning. It has been shown to be of clinical value for patients both in the primary and secondary stages of prostate cancer. The aim of this study was to determine the effective dose and organ doses from injection of [⁶⁸Ga]PSMA-11 in a cohort of low-risk prostate cancer patients.

Methods: Six low-risk prostate cancer patients were injected with 133-178 MBq [⁶⁸Ga]PSMA-11 and examined with four PET/CT acquisitions from injection to 255 min post-injection. Urine was collected up to 4 h post-injection, and venous blood samples were drawn at 45 min, 85 min, 175 min, and 245 min post-injection. Kidneys, liver, lungs, spleen, salivary and lacrimal glands, and total body where delineated, and cumulated activities and absorbed organ doses calculated. The software IDAC-Dose 2.1 was used to calculate absorbed organ doses according to the International Commission on Radiological Protection (ICRP) publication 107 using specific absorbed fractions published in ICRP 133 and effective dose according to ICRP Publication 103. We also estimated the absorbed dose to the eye lenses using Monte Carlo methods.

Results: [⁶⁸Ga]PSMA-11 was rapidly cleared from the blood and accumulated preferentially in the kidneys and the liver. The substance has a biological half-life in blood of 6.5 min (91%) and 4.4 h (9%). The effective dose was calculated to 0.022 mSv/MBq. The kidneys received approximately 40 mGy after an injection with 160 MBq [⁶⁸Ga]PSMA-11 while the lacrimal glands obtained an absorbed dose of 0.12 mGy per administered MBq. Regarding the eye lenses, the absorbed dose was low (0.0051 mGy/MBq).

Conclusion: The effective dose for [⁶⁸Ga]PSMA-11 is 0.022 mSv/MBq, where the kidneys and lacrimal glands receiving the highest organ dose.

Keywords: Absorbed dose and effective dose; Glu-NH-CO-NH-Lys(Ahx)-HBED-CC; PET-tracer; PSMA; Prostate cancer; Radiation dosimetry; [68Ga]PSMA-11.