Bendamustine Plus Bortezomib Plus Dexamethasone in Relapsed or Refractory Multiple Myeloma

Inclusion Criteria: * Age min. 18 years at the time of signing the informed consent form * Life expectancy of at least 3 months * Able to adhere to the study visit schedule and other protocol requirements * Measurable disease, defined as any quantifiable monoclonal protein value, defined by at least one of the following three measurements: Serum M-protein ≥ 10g/l; Urine light-chain (M-protein) of ≥ 200 mg/24 hours; Serum FLC assay: involved FLC level ≥10 mg/dl provided sFLC ratio is abnormal * Relapsed or refractory MM in stage II or III after autologous SCT or conventional chemotherapy (histologically or cytologically proven/ Salmon and Durie criteria) in need of therapy * All previous cancer therapy, including cytostatic therapy and surgery, must have been discontinued at least 4 weeks prior to treatment in this study, except corticosteroid therapy (dosage 40 to max. 160mg). Localised radiation therapy is allowed, but the increased risk of leukocytopenia, erythrocytopenia and thrombocytopenia based on the combination of a polychemotherapy and radiation therapy has to be considered and a close monitoring of the patients has to be assured. * ECOG performance status of 0-2 at study entry * Laboratory test results within these ranges: * Absolute neutrophil count min. 1.5 x 109/L * Platelet count min. 75 x 109/L * Total bilirubin max. 1.5 mg/dL * AST (SGOT) and ALT (SGPT) max. 2 x ULN or max. 5 x ULN if hepatic lesions are present. * Disease free of prior malignancies for min. 5 years with exception of curatively treated basal cell, squamous cell carcinoma of the skin, or carcinoma "in situ" of the cervix or breast * Fertile patients must use effective contraception during and for 6 months after study treatment No study treatment or any other procedure within the framework of the trial (except for screening) will be performed in any patient prior to receipt of written informed consent. Exclusion Criteria: * Any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from signing the informed consent form * Pregnant or breast feeding females * Any condition, including the presence of laboratory abnormalities, which places the subject at unacceptable risk if he/she were to participate in the study or confounds the ability to interpret data from the study. * Peripheral neuropathy or neuropathic pain of grade 2 or greater intensity, as defined by NCI CTCAE, version 3.0. * Use of any other experimental drug or therapy within 28 days of pre-study visit. * Known hypersensitivity to the study drugs * Any prior use of bortezomib or bendamustine in the last six months * Concurrent use of other anti-cancer agents or treatments other than those stated in this treatment plan * Known positive for HIV or infectious hepatitis, type A, B or C * Active, uncontrolled infections * Acute diffuse infiltrative pulmonary disease and pericardial disease.