Melphalan and Busulfan Followed By Donor Peripheral Stem Cell Transplant, Tacrolimus, and Methotrexate in Treating Patients With Multiple Myeloma

DISEASE CHARACTERISTICS: Diagnosis of multiple myeloma Stage I disease with disease progression during the second of ≥ 2 lines of prior therapy Stage II or III disease, meeting 1 of the following criteria: Failed to achieve at least a partial response after ≥ 2 courses of prior therapy Progressive disease after ≥ 2 courses of prior therapy Presented with high-risk features at diagnosis, including any of the following: Cytogenetic abnormality Del 13 or 4,14 by fluorescent in situ hybridization (FISH) Elevated lactic dehydrogenase Beta 2 microglobulin > 5.5 Circulating peripheral blood plasma cells Any stage disease with disease progression > 6 months after prior autologous stem cell transplantation Availability of an HLA-matched, related donor between 12 and 75 years of age* No bone marrow donors NOTE: *Donors > 75 years of age are eligible at the discretion of the principal investigator PATIENT CHARACTERISTICS: Karnofsky performance status 70-100% Creatinine clearance > 60 mL/min Bilirubin ≤ 2.5 mg/dL ALT/AST < 2 times upper limit of normal Cardiac ejection fraction ≥ 49% DLCO ≥ 50% corrected FEV_1 ≥ 60% Not pregnant or nursing Fertile patients must use effective contraception HIV negative No cirrhosis No chronic inflammatory or fibrotic liver disease PRIOR CONCURRENT THERAPY: See Disease Characteristics At least 6 months since prior autologous transplantation