Safety will be evaluated by vital signs (blood pressure, heart rate, respiratory rate and temperature), physical examinations, electrocardiograms (EKGs), clinical laboratory tests and adverse event monitoring. Laboratory studies will include hematology, chemistry and urinalysis at baseline, at the end of the inpatient treatment period, and at 2 weeks and 6 weeks after the infusion of the 188Re-PTI-6D2 dose. If hematological recovery has not occurred by week 6, patients will follow-up monthly until hematological recovery. In addition, thyroid function tests will be performed at baseline and at 6 weeks after infusion; then monthly until recovery (if has not occurred). Human anti-murine antibodies (HAMA) will be measured at baseline, 2 weeks, and 6 weeks after infusion .