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 [Note: classification removed under
current WHO classification system]), refractory cytopenia with multilineage dysplasia
(RCMD), RCMD with ringed sideroblasts (RCMD-RS), or chronic myelomonocytic leukemia
(CMML)

- Patients in relapse must have documented CD45 expression by their myelodysplastic or
leukemic cells to be studied and treated with 131I-labeled BC8 antibody; 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 undergo a 24-hour urine collection with documented creatinine clearance
> 50 ml/min

- Patients must have normal hepatic function (bilirubin, AST and ALT < 2 times the
upper limit of normal)

- Karnofsky score >= 70 or 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 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 FHCRC Standard Practice
Guidelines and to the allele level at DQB1; 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; PBSC is the only permitted HSC source

- DONOR: Donors must meet HLA matching criteria as outlined above as well as standard
SCCA and/or NMDP criteria for PBSC donation

Exclusion Criteria:

- Circulating antibody against mouse immunoglobulin (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 HIV

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

- Patients who have previously undergone marrow or PBSC transplantation