A radioimmunoconjugate consisting of a chimeric monoclonal antibody targeting human cadherin-3 (CDH3) and labeled, via the macrocyclic chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), with the beta-emitting radioisotope yttrium Y 90, with potential antineoplastic activities. Upon administration, the antibody moiety of yttrium Y 90 anti-CDH3 monoclonal antibody FF-21101 binds to CDH3 expressed on tumor cells, thereby specifically delivering cytotoxic beta radiation to CDH3-expressing tumor cells. CDH3, also known as P-cadherin, is a tumor-associated antigen (TAA) and member of the cadherin family; it is overexpressed in a variety of tumors and plays a role in cell adhesion, motility, invasion, and proliferation.