Fludarabine and Radiation Therapy in Treating Patients Who Are Undergoing Donor Stem Cell Transplant for Chronic Phase or Accelerated Phase Chronic Myelogenous Leukemia

DISEASE CHARACTERISTICS: * Diagnosis of Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia, meeting 1 of the following criteria: * Chronic phase * Ph+ by cytogenetics or fluorescent in situ hybridization (FISH) assay * Accelerated phase, meeting any of the following criteria: * More than 10% but \< 30% myeloblasts and promyelocytes in marrow or peripheral blood * Any additional clonal cytogenetic abnormalities * Increasing splenomegaly * Extramedullary tumor * WBC, platelet count, or hematocrit perturbations not controlled by therapy with hydroxyurea, interferon, or imatinib mesylate * Persistent unexplained fever or bone pain * Less than 5% blasts in the marrow at time of transplantation * Not eligible for OR refused conventional myeloablative allogeneic stem cell transplantation * Failed OR suboptimal response to prior imatinib mesylate, as defined by 1 of the following: * Absence of complete hematologic response after \> 3 months of treatment with imatinib mesylate * Absence of cytogenetic response, as defined by 1 of the following: * Absence of any cytogenetic response (\< 95% Ph+ or BCR/ABL+ cells by cytogenetic or FISH analysis, respectively) after 6 months of treatment with imatinib mesylate * Absence of major cytogenetic response (\< 35% Ph+ or BCR/ABL+ cells by cytogenetic or FISH analysis, respectively) after 1 year of treatment with imatinib mesylate * Absence of complete cytogenetic response (no Ph+ cells by cytogenetic analysis OR BCR/ABL+ cells within normal limits by FISH analysis) after 18 months of treatment with imatinib mesylate * Hematologic evidence of disease progression * Cytogenetic evidence of disease progression * Increase in Ph+ cells or BCR/ABL+ cells by \> 20% with at least 1 month between sequential testing * Molecular evidence of disease progression * More than 10-fold increase in BCR/ABL mRNA levels by quantitative polymerase chain reaction (Q-PCR) with at least 1 month between 2 sequential tests * Experienced adverse events during treatment with imatinib mesylate that precluded further administration of the drug * No CNS disease refractory to intrathecal chemotherapy * HLA identical related donor available * Phenotypically matched at HLA-A, -B, -C, DRQ1, and DBQ1 * No presence of circulating leukemic blasts by standard pathology PATIENT CHARACTERISTICS: Age * Any age Performance status * Karnofsky 70-100% OR * Lansky 70-100% Life expectancy * Not specified Hematopoietic * See Disease Characteristics Hepatic * No fulminant liver failure * No cirrhosis of the liver with evidence of portal hypertension or bridging fibrosis * No alcoholic hepatitis * No esophageal varices * No history of bleeding esophageal varices * No hepatic encephalopathy * No uncorrectable hepatic synthetic dysfunction evidenced by prolongation of PT * No ascites related to portal hypertension * No bacterial or fungal liver abscess * No biliary obstruction * No chronic viral hepatitis AND bilirubin \> 3 mg/dL * No symptomatic biliary disease Renal * Renal failure allowed Cardiovascular * No symptomatic coronary artery disease * Ejection fraction ≥ 35% * No other cardiac failure requiring therapy * No poorly controlled hypertension (blood pressure ≥ 150/90 mm Hg) on standard medication Pulmonary * DLCO ≥ 30% * Total lung capacity ≥ 30% * FEV\_1 ≥ 30% * No requirement for continuous supplementary oxygen * No fungal pneumonia with radiological progression after treatment with amphotericin or mold-active azoles for \> 1 month Other * Not pregnant or nursing * Fertile patients must use effective barrier contraception during and for 12 months after completion of study treatment * HIV negative * No other disease that severely limits life expectancy * No other active malignancy except localized nonmelanoma skin cancer * No nonhematologic malignancy within the past 5 years that is currently in complete remission and has a \> 20% risk of disease recurrence except for nonmelanoma skin cancer * No systemic uncontrolled infection * No active bacterial or fungal infection unresponsive to medical therapy PRIOR CONCURRENT THERAPY: Biologic therapy * See Disease Characteristics Chemotherapy * See Disease Characteristics Endocrine therapy * Not specified Radiotherapy * Not specified Surgery * Not specified Other * At least 48 hours since prior imatinib mesylate