A radioconjugate of biotin and yttrium Y 90 (Y-90) linked through the bifunctional macrocyclic chelating agent tetra-azacyclododecanetetra-acetic acid (DOTA) with radioimmunotherapy property. Biotin is a water-soluble B-complex vitamin, present in minute amounts in every living cell, while its level in cancerous tissue is higher than that of normal tissue. Y 90-DOTA-biotin could be used in 3-step pre-targeting radioimmunotherapy that employs a tumor targeting antibody conjugated with streptavidin, the natural ligand of biotin. OR A compound that contains the radioisotope yttrium Y 90 linked to the chemical biotin. Biotin is a molecule that binds strongly to the chemical streptavidin. Yttrium Y 90 DOTA-biotin will find tumor cells in the body that have been targeted by an antibody linked to streptavidin and kill them. It is being studied together with CC49-streptavidin in the treatment of cancer. Also called 90Y-DOTA-biotin.