PURPOSE: To evaluate therapeutic strategies, it is essential to use biological models reflecting important aspects of the clinical situation. The aim of the present study was to compare the maximal tolerable dose of the monoclonal antibody BR96 labeled with 90Y or 177Lu in immunocompetent rats. Maximal tolerable dose was defined as the highest activity that allows 100% of the animals to survive without clinical signs, such as infections, bleeding, or diarrhea, and with