Dosimetric Support of Radionuclide Therapy

Abstract

Purpose: Analysis of modern approaches to dosimetric support of radionuclide therapy at the technological stages of dosimetric planning, hospitalization in a hospital and evaluation of treatment eծectiveness.Material and methods: A comparative analysis of the methodological specifics of the dosimetric support of radionuclide therapy with the introduction of radiopharmaceuticals into the body and conventional radiation therapy using sealed sources of ionizing radiation was carried out.Two methodically different approaches to dosimetric planning of the level of internal exposure from a radiopharmaceutical introduced into the patient’s body are considered.The features of radiation monitoring are discussed both for the patient’s stay in the radionuclide therapy department and for safe discharge from the department for others, and for the solid and liquid radioactive waste being removed.A comparative analysis of the functionality of various criteria for assessing the long-term and short-term effectiveness of radionuclide therapy for bone metastases was carried out.Focal absorbed doses of internal exposure are considered as one of the criteria, for the determination of which a simplified method for their calculation is proposed based on quantitative data from SPECT/CT scanning of an X-ray phantom and a real patient who has been injected with a β-γ-emitting therapeutic radiopharmaceutical.Results: On a clinical example of radionuclide therapy with 177Lu-PSMA-617 in a patient with stage 4 prostate cancer, dose estimates of internal irradiation of foci with β-particles were obtained. Calculations were made for bone metastases of 7 localizations in dynamics for each of the 5 fractions of the course of radionuclide therapy. It is shown that the total focal doses for 5 fractions of internal exposure vary from 70.6 to 116.8 Gy for different foci, which corresponds to the literature data obtained by more accurate methods of dosimetry of internal exposure. The obtained dosimetric data were compared with efficacy estimates based on metabolic, hematological, hormonal and biochemical parameters, as well as on the tumor marker PSA.Conclusion: In contrast to conventional radiation therapy, dosimetric support for planning and evaluating the effectiveness of treatment has not yet become the fundamental methodological basis of modern radionuclide therapy.