Therapeutic dose: Groups of 3-6 subjects were enrolled at successively higher whole-body radiation dose levels beginning at a total body dose (TBD) of 25 centiGray (cGy). The TBD of each subsequent dose level was escalated by 10 cGy. Subjects who had undergone bone marrow transplantation (BMT) underwent a separate dose escalation (10 cGy TBD increase per dose level) beginning at a TBD level of 65 cGy. The MTD was defined as the highest dose level at which 0/3 or 1/6 subjects experienced dose-limiting toxicity (DLT).