Methods of dosimetry-based treatment planning in radiopharmaceutical therapy. Part 2: Planning levels

At the present time three most common approaches are used for the planning of the radionuclide therapy: administration of the fixed activity of radionuclide in radiopharmaceutical, or administration of activity normalized per unit of body mass or body surface. That may lead to significant deviations between the prescribed and real absorbed doses in healthy organs and tissues. These deviations are associated with differences in biodistribution and pharmacokinetics of radiopharmaceutical between models and real patients. That does not allow individual planning of the treatment course for each patient since data on the accumulated activity in source regions and organs at risk is limited and uncertainty is too high for the calculation of absorbed doses. Improvements in the reliability of the absorbed dose calculation can be achieved through the use of different imaging modalities (diagnostic nuclear medicine) for the quantitative assessment of accumulated activity of radionuclides in organs and tissues and distribution of radiopharmaceutical in healthy tissues. Planning of radionuclide therapy should be personalized. The current study was aimed at the analysis of the approaches the dosimetry-based planning of radionuclide therapy presented in the Report of International Commission on Radiation Units and Measurements 96 «Dosimetry-guided radiopharmaceutical therapy», differentiated based on the possibilities of the nuclear medicine departments, including examples of levels of planning for most common radiopharmaceuticals. The results of analysis indicated that most optimal approach for Russian clinical practice is to transit to the requirements of planning level 1: to calculate and report administered activity considering patient body mass, type and stage of disease was well as prescribed clinical task. Requirements of planning level 2 are currently impossible to implement nation-wide, except for several nuclear medicine research facilities. Additionally, it is necessary to focus on the development of the methods of estimation of absorbed doses in major delineable organs.

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