A Phase I Study of Bendamustine and Melphalan Conditioning and Autologous Stem Cell Transplantation for Treatment of Multiple Myeloma and Relapsed/Refractory B-cell Lymphoma in Elderly Patients

Inclusion Criteria: Phase I eligibility: * Any patient with multiple myeloma B-cell non-Hodgkin lymphoma would be eligible for phase I portion of the study. Dose expansion eligibility: * Histologically confirmed diagnosis of multiple myeloma or rel/ref DLBCL, or diffuse large B cell lymphoma transformed from an indolent lymphoma Since the endpoint of the Phase I portion is safety, any patient with myeloma or B-cell NHL can be enrolled. For dose expansion study patients with myeloma and B-NHL will be analyzed separately. The PFS endpoint varies greatly amongst different types of lymphoma. In order to accurately interpret the survival data as secondary endpoint, a homogeneous cohort of patients with DLBCL will be evaluated. DLBCL is the most aggressive B-NHL with limited options. Other B-NHL's are generally more indolent and have more options available to them. Additional eligibility for both the phase I and dose expansion cohort: * Patients between the ages of 65 to 69 years old with a Hematopoietic Stem Cell Transplant Comorbidity Index (HCT-CI) score of 3 or higher. * Any patient age 70 years old or older, irrespective of their Hematopoietic Stem Cell Transplant Comorbidity Index (HCT-CI) score. * KPS ≥ 70 * Males must agree to use an acceptable form of contraception per institutional practices. * Complete or partial response to salvage chemotherapy by IWG Working Group Criteria * Cardiac ejection fraction of ≥ 45% * Hemoglobin-adjusted diffusing capacity of carbon monoxide (DLCO) of ≥45% * Creatinine clearance of ≥50 mL/min * Completion of most recent salvage therapy within 8 weeks of enrollment * Direct bilirubin ≤2.0 mg/dL in the absence of suspected Gilbert's disease (if Gilbert's disease is suspected, the total bilirubin must be ≤3.0 mg/dL), and AST ≤ 2.5 ULN. Exclusion Criteria: * In Lymphoma: Disease progression by IWG Working Group Criteria since last therapy * Patients with history of CNS involvement * Prior autologous (only in lymphoma) or allogeneic stem cell transplantation * Patients who have failed bendamustine-based regimen previously * Patients within 6 months of MI and stroke will be excluded