A substance being studied in the treatment of some types of cancer. Yttrium Y 90 SMT 487 contains a molecule that binds to a protein found on certain types of neuroendocrine tumors (tumors that form from cells that release hormones). It also contains a radioactive substance called yttrium Y 90, which may help kill cancer cells. Yttrium Y 90 SMT 487 is a type of radioconjugate. Also called yttrium Y 90 DOTA-tyr3-octreotide and yttrium Y 90 edotreotide.