Methods of dosimetry-based treatment planning in radiopharmaceutical therapy. Part 1: terminology and definitions

Existing drawbacks of the radionuclide therapy planning may lead to the excessive irradiation of the healthy organs and tissues that is associated with the development of deterministic and stochastic effects. In some cases absorbed dose in region of interest (lesion) can be lower than prescribed therapeutic dose. That reduces the effectiveness of radionuclide therapy and reduces survival rate of patients. These problems are associated with administration of the fixed activity of radionuclide in radiopharmaceutical, or administration of activity normalized per unit of body mass or body surface. That approach does not allow assessing absorbed doses in lesions or healthy tissues for individual patients. Report of International Commission on Radiation Units and Measurements 96 «Dosimetry-guided radiopharmaceutical therapy», published in 2021, presents modern approaches for the dosimetric planning of radionuclide therapy based on the individualized assessment of absorbed doses in organs and tissues. This study was aimed at the analysis of proposed in Report 96 methods of classification of irradiated regions, organs and tissues based on example of radionuclide therapy with ¹⁷⁷Lu-DOTATATE. Proposed terms and definitions are harmonized with previous reports of International Commission on Radiation Units and Measurements on external radiation therapy. Terms and definitions analyzed in the current study will be used in the following studies aimed at the development of the requirements on dosimetric planning of radionuclide therapy.

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