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

RATIONALE: Giving low doses of chemotherapy, such as fludarabine, and radiation therapy before a donor peripheral blood stem cell transplant helps stop the growth of cancer cells. It also stops the patient's immune system from rejecting the donor's stem cells. The donated stem cells may replace the patient's immune system and help destroy any remaining cancer cells (graft-versus-tumor effect). Giving an infusion of the donor's T cells (donor lymphocyte infusion) or interferon alfa after the transplant may help increase this effect. Sometimes the transplanted cells from a donor can also make an immune response against the body's normal cells. Giving cyclosporine and mycophenolate mofetil after the transplant may stop this from happening. PURPOSE: This phase II trial is studying how well giving fludarabine together with radiation therapy works in treating patients who are undergoing donor stem cell transplant for chronic phase or accelerated phase chronic myelogenous leukemia.

OBJECTIVES: Primary * Determine the disease-free survival rate in patients with chronic or accelerated phase chronic myelogenous leukemia that failed or inadequately responded to prior imatinib mesylate treated with nonmyeloablative conditioning comprising fludarabine and low-dose total-body irradiation followed by allogeneic peripheral blood stem cell transplantation. Secondary * Determine the complete cytogenetic and molecular response rates in patients treated with this regimen. * Determine overall survival of patients treated with this regimen. * Determine non-relapse mortality in patients treated with this regimen. * Determine the incidence of serious infection, graft-versus-host disease, and myelosuppression in patients treated with this regimen. OUTLINE: This is a multicenter study. * Conditioning treatment: Patients receive fludarabine IV on days -4 to -2. Patients undergo low-dose total-body irradiation (TBI) on day 0. * Allogeneic peripheral blood stem cell transplantation: After TBI, patients undergo allogeneic peripheral blood stem cell transplantation on day 0. * Immunosuppression: Patients receive oral cyclosporine twice daily on days -3 to 56 followed by a taper to day 180 in the absence of graft-versus-host disease (GVHD). Patients also receive oral mycophenolate mofetil twice daily on days 0-27. * Post-transplant treatment: Patients experiencing disease persistence or progression AND low donor chimerism discontinue immunosuppression. Patients with disease persistence or progression after discontinuing immunosuppression receive oral imatinib mesylate once daily. Patients who have disease improvement after day 28 of imatinib mesylate treatment AND who have no evidence of disease after day 84 of imatinib mesylate treatment continue imatinib mesylate in the absence of disease progression or unacceptable toxicity. Patients who fail to improve after day 28 of imatinib mesylate treatment OR who have residual disease after day 84 of imatinib mesylate treatment receive donor lymphocytes IV over 15-30 minutes once every 1-4 months for up to 4 infusions. Patients ineligible to receive donor lymphocytes (e.g., patients with evidence of GVHD) receive interferon alfa subcutaneously 3 times a week for up to 12 months in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed at 6, 9, 12, 18, and 24 months, and then annually for 5 years. PROJECTED ACCRUAL: A total of 40 patients will be accrued for this study.