RATIONALE: Giving chemotherapy before a donor stem cell transplant helps stop the growth of cancer or abnormal cells. It also helps stop the patient's immune system from rejecting the donor's stem cells. When the healthy stem cells from a donor are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. Sometimes the transplanted cells from a donor can make an immune response against the body's normal cells. Giving cyclosporine and methotrexate before and after transplant may stop this from happening.

PURPOSE: This clinical trial is studying the side effects and how well donor stem cell transplant works when given after conditioning therapy in treating patients with hematologic cancer, recurrent or metastatic solid tumor, or other disease.

OBJECTIVES:

• Determine the safety and efficacy of non-T-cell depleted, HLA-haploidentical related donor hematopoietic stem cell transplantation after a reduced-intensity conditioning regimen comprising busulfan, fludarabine phosphate, anti-thymocyte globulin, and methylprednisolone in patients with hematologic cancer, recurrent or metastatic solid tumors, or other diseases.

OUTLINE:

• Reduced-intensity conditioning regimen: Patients receive busulfan IV 4 times daily on days -7 and -6; fludarabine phosphate IV over 30 minutes on days -7 to -2; and methylprednisolone IV over 30 minutes followed by anti-thymocyte globulin IV over 4 hours on days -4 to -1.
• Donor hematopoietic stem cell transplantation: Patients receive donor peripheral blood stem cells IV over 1 hour on days 0 and 1.
• Graft-versus-host disease (GVHD) prophylaxis: Patients receive cyclosporine IV over 2-4 hours or orally twice daily beginning on day -1 and continuing until day 60, followed by a taper in the absence of GVHD. Patients also receive methotrexate IV on days 2, 4, 7, and 12.

After the transplant, patients are followed periodically.

DISEASE CHARACTERISTICS:

• Diagnosis of 1 of the following:

  • High-risk acute leukemia, including any of the following:

    • Refractory acute leukemia
    • Acute leukemia beyond first remission
    • Acute leukemia in first remission with poor prognostic features (e.g., chromosomal changes suggesting poor prognosis)

  • Chronic myelogenous leukemia in second chronic, accelerated, or blastic phase

  • Severe aplastic anemia that is not responsive to immunosuppressive therapy

  • Myelodysplastic syndromes, including any of the following:

    • Refractory anemia (RA) or RA with ringed sideroblasts with severe cytopenia
    • RA with excess blasts (RAEB)
    • RAEB in transformation
    • Chronic myelomonocytic leukemia

  • Refractory or relapsed non-Hodgkin or Hodgkin lymphoma

  • Multiple myeloma

  • Biopsy proven measurable solid tumor meeting 1 of the following criteria:

    • Recurrent disease after primary treatment and deemed incurable to standard treatment
    • Metastatic disease for which no known standard therapy that is potentially curative or definitely capable of extending life expectancy exists

• Must have a related HLA-haploidentical mismatched (3/6 or fewer loci) donor available

PATIENT CHARACTERISTICS:

• Karnofsky performance status 70-100%
• Bilirubin < 2.0 mg/dL
• AST < 3 times upper limit of normal
• Creatinine < 2.0 mg/dL
• Ejection fraction > 40% by MUGA

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics