OUTLINE: This is a dose-escalation study. All patients receive a test dose of iodine I 131 monoclonal antibody BC8 (MOAB BC8) IV over several hours 6-14 days prior to the therapeutic dose. Patients receive the therapeutic dose of iodine I 131 MOAB BC8 IV over several hours on day -11, total body irradiation over 30-40 minutes twice a day on days -6 to -4, and cyclophosphamide IV over 1 hour on days -3 and -2. Patients undergo allogenic bone marrow transplantation on day 0. Patients receive intrathecal methotrexate twice prior to transplantation and then every other week for 4 weeks beginning on day 32 posttransplant. Cohorts of 4 patients receive escalating doses of iodine I 131 monoclonal antibody until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 4 patients experience dose-limiting toxicity. Patients are followed for the first 100 days, at 6, 9 and 12 months, every 6 months for 1 year, and then annually thereafter.