"Therapeutic Dose", Groups of 3-6 subjects were treated at successively higher therapeutic whole body radiation doses, beginning at a TBD of 25 cGy. The TBD was escalated in 10 cGy increments in subsequent dose level cohorts until the MTD was achieved. A separate determination of MTD was conducted for subjects who had undergone prior BMT. This was initiated at a TBD of 65 cGy TBD and increased in 10 cGy increments until determination of the MTD. The MTD was defined as the dose at which fewer than 1/3 or 2/6 subjects experienced DLT, i.e. any Grade 4 hematologic toxicity (absolute neutrophil count [ANC], platelets, hemoglobin, white blood count [WBC] lasting > 7 days or any Grade 3 hematologic toxicity lasting > 14 days, as defined in Section 4.1.