Dose evaluation of therapeutic radiolabeled bleomycin complexes based on biodistribution data in wild-type rats: Effect of radionuclides in absorbed dose of different organs

Bleomycins (BLMs), as tumor-seeking antibiotics, have been used for over 20 years in treatment of several types of cancers. Several radioisotopes are used in radiolabeling of BLMs for therapeutic and diagnostic purposes. An important points in developing new radiopharmaceuticals, especially therapeutic agents, is the absorbed dose delivered in critical organs. In this work, absorbed dose to organs after injection of ¹⁵³Sm-, ¹⁷⁷Lu- and ¹⁶⁶Ho-labeled BLM was investigated by radiation dose assessment resource (RADAR) method based on biodistribution data in wild-type rats. The absorbed dose effect of the radionuclides was evaluated. The maximum absorbed dose for the complexes was observed in the kidneys, liver and lungs. For all the radiolabeled BLMs, bone and red marrow received considerable absorbed dose. Due to the high energy beta particles emitted by ¹⁶⁶Ho, higher absorbed dose is observed for ¹⁶⁶Ho-BLM in the most organs. The reported data can be useful for the determination of the maximum permissible injected activity of the radiolabeled BLMs in the treatment planning programs. (authors)