Inclusion Criteria:

- Patients with advanced AML defined as beyond first remission, primary refractory
disease, or evolved from myelodysplastic or myeloproliferative syndromes; or patients
with MDS expressed as refractory anemia with excess blasts (RAEB), refractory anemia
with excess blasts in transformation (RAEBT), refractory cytopenia with multilineage
dysplasia (RCMD), RCMD with ringed sideroblasts (RCMD-RS), or chronic myelomonocytic
leukemia (CMML)

- Patients not in remission must have cluster of differentiation (CD)45-expressing
leukemic blasts or myelodysplastic cells; patients in remission do not require
phenotyping and may have leukemia previously documented to be CD45 negative (because
in remission patients, virtually all antibody binding is to non-malignant cells which
make up > 95% of nucleated cells in the marrow)

- Patients should have a circulating blast count of less than 10,000/mm^3 (control with
hydroxyurea or similar agent is allowed)

- Patients must have an estimated creatinine clearance greater than 50/ml per minute
(serum creatinine value must be within 28 days prior to registration)

- Bilirubin < 2 times the upper limit of normal

- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) < 2 times the
upper limit of normal

- Karnofsky score >= 70 or Eastern Cooperative Oncology Group (ECOG) =< 2

- Patients must have an expected survival of > 60 days and must be free of active
infection

- Patients must have an HLA-identical sibling donor or an HLA-matched unrelated donor
who meets standard Seattle Cancer Care Alliance (SCCA) and/or National Marrow Donor
Program (NMDP) criteria for PBSC donation; related donors should be matched by
molecular methods at the intermediate resolution level at HLA-A, B, C, and DRB1
according to Fred Hutchinson Cancer Research Center (FHCRC) Standard Practice
Guidelines and to the allele level at DQB; unrelated donors should be identified
using matching criteria that follows the FHCRC Standard Practice Guidelines limiting
the study to eligible donors that are allele matched for HLA-A, B, C, DRB1, and DQB1
(Grade 1), and accepting up to one allele mismatch as per Standard Practice Grade 2.1
for HLA-A, B, or C

Exclusion Criteria:

- Circulating antibody against mouse immunoglobulin (human anti-mouse antibody [HAMA])

- Prior radiation to maximally tolerated levels to any normal organ

- Patients may not have symptomatic coronary artery disease and may not be on cardiac
medications for anti-arrhythmic or inotropic effects

- Inability to understand or give an informed consent

- Patients who are seropositive for human immunodeficiency virus (HIV)

- Perceived inability to tolerate diagnostic or therapeutic procedures, particularly
treatment in radiation isolation

- Patients who have previously undergone autologous or allogeneic HSCT