Effect of administration route on the biodistribution of albumin microspheres labelled with Re-188

Nowadays the radiolabeled microspheres are established tools for radioembolization of primary and metastatic liver cancer. Human serum albumin microspheres (HSA) are unique carriers for selective and controlled radionuclide delivery to malignant tumors. Rhenium-188 (Re-188), which decays with beta particles (2.12 MeV (71.1%) and 1.965 MeV (25.6%) and gamma emission (155 keV (15.1%)) is one of the most available and promising generator-based radionuclide for cancer therapy. The purpose of this work was to study the biodistribution of microspheres based on hu-man serum albumin labeled with Re-188 (Re-188-HSA) in animals after different routes of admin-istration. The size of more than 95% of microspheres was 10-20 μm. The studies were carried out on outbred white mice and inbred C57BL/6 mice with transplanted Lewis adenocarcinoma after intravenous, intramuscular and intratumoral administration. After intravenous injection the high-est amount of Re-188-HSA in organs and tissues was observed: up to 311.3%/g in lungs, up to 74.30%/g in thyroid gland, up to 12.70%/g in liver, up to 0,81%/g in blood. After the intramuscular injection of 188Re-HSA, the concentration of 188Re-HSA in organs and tissues was significantly lower and did not exceed 1%/g, except for thyroid gland (1,10-17.80%/g). After intratumoral injec-tion the amount of Re-188-HSA in tumor varied from 16.7 to 26.8%/g, that was higher as compared with other organs and tissues. Thus, the routes of Re-188-HSA administration significantly affect its behavior in the body. The obtained results can be used to evaluate the Re-188-HSA potential for radionuclide tumor therapy after intravascular or intratumoral administration.