 This is a prospective, multi-centre, randomized the study drug is assigned by chance, controlled, open-label all people involved in the study know the identity of the assigned drug, parallel each group of patients will be treated at the same time group phase III study to determine the efficacy of the standard therapy of bortezomib and low dose dexamethasone in combination with or without continuous low dose oral cyclophosphamide for primary refractory or relapsed myeloma patients 1st - 3rd relapse. The study will consist of screening period, which may last from day -14 until day -1 before application of the first dose of bortezomib on cycle 1, day 1, treatment phase begins on cycle 1 day 1 and continues until completion or discontinuation of all study drugs and follow-up phase. All patients will be followed up after end of treatment regardless of their response. Eligible patients will be randomized in 1:1 ratio to receive either treatment arms Group A: receiving bortezomib plus dexamethasone or Group B receiving bortezomib plus dexamethasone plus cyclophosphamide. Patients will receive up to eight 3-weeks treatment cycles, unless they experience either unacceptable toxicity or if the patients request to withdraw from the study. The maximum number of cycles is dependent on patient response and investigators discretion. It is recommended that patients with a confirmed complete response CR receive 2 additional cycles beyond a confirmation. Patients who do not achieve a CR but a partial response will receive a total of 8 cycles. For patients achieving stable disease it is within the investigators discretion to continue study treatment beyond 6 cycles, after discussion with the sponsor. After completion of treatment the patients will be followed up every 12 weeks for up to 72 weeks. If the study is still ongoing a further follow up period will be done every 26 weeks until study end, or until the patient reaches progressive disease or start of alternative anti-myeloma therapy, if earlier. In case progressive disease PD has already been established during the treatment phase the patients will not enter the follow-up phase. In case of PD or start of alternative anti-myeloma treatment before the end of study the follow-up phase will be discontinued for the patient but the date of death of the patient will be documented if applicable before the end of study. 