Blood and urine specimens are collected periodically over a 6-week period following the infusion to determine the level of the radioactive antibody. Bone marrow, lymph node, or skin biopsies may be done to determine how much of the antibody entered these sites. Patients whose disease remains stable or improves with therapy may receive up to six more infusions of 90 Y-HAT, with at least a 6-week interval between treatments.