Radiation dosimetry for indium-111-labeled anti-CEA-F(ab')2 fragments evaluated from tissue distribution in rats

Accurate dosimetric investigations are important to be able to fulfill the ambition of radiation protection in nuclear medicine and to minimize the radiation burden to the patient. This paper presents human radiation absorbed dose estimates following an administration of an 111In-labeled anti-CEA-F(ab')2 (BW431/31) based on detailed biodistribution and elimination data in a rat model. Animals were followed from the time of injection up to 28 days after injection. A significant initial uptake of 111In in the bone marrow, 25% of injected activity, was evident after 6 hr. The kidneys showed a maximal uptake of 20% at 24 hr. At the end of the study, 27% of the activity was still retained in the whole body. The estimated humans absorbed dose to the kidneys, testes, spleen and bone marrow was 2.27, 0.80, 0.51 and 0.37 mGy MBq-1, respectively. The effective dose was estimated to 0.27 mSv MBq-1. The tissue distribution in rats was comparable to that in humans, which was confirmed by whole-body scintigrams and human biopsies.