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

Mol Imaging Biol. 2016 Jun;18(3):437-45. doi: 10.1007/s11307-016-0942-0.

Abstract

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.

Conclusion: 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.

Keywords: Dosimetry; Lacrimal glands; PSMA; Prostate cancer; Radioligand radiation therapy.

MeSH terms

  • Aged
  • Demography
  • Dose-Response Relationship, Radiation
  • Humans
  • Lacrimal Apparatus / diagnostic imaging*
  • Male
  • Middle Aged
  • Organometallic Compounds / chemistry*
  • Organs at Risk / radiation effects*
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / radiotherapy*
  • Time Factors
  • Tissue Distribution / radiation effects
  • Whole Body Imaging

Substances

  • 177Lu-DKFZ-PSMA-617
  • Organometallic Compounds