Patients with multiple myeloma that are refractory to or have relapsed/progressed after primary treatment for multiple myeloma will be enrolled in the study. All patients will receive a combination of bortezomib plus dexamethasone for a total of four cycles. Based on the response to this treatment, further study treatment is customized. Patients with a complete, a very good partial or a partial response will continue to receive bortezomib and Dexamethasone for a maximum additional four cycles, to an overall maximum of eight cycles. Patients achieving stable disease, as defined by International Myeloma Working Group 2006 (IMWG 2006) response criteria, will undergo a central randomisation to continue treatment with VD or VD plus cyclophosphamide or VD plus lenalidomide. Patients with progressive disease will go off study treatment. After randomisation, patients will receive therapy for up to four additional treatment cycles, to an overall maximum of eight cycles. Each cycle will consist of three weeks treatment. There will be a long-term follow-up period with monthly visits until relapse or progressive disease. Thereafter follow-up for survival will be continued by at least a phone call every other month. This will be performed for all patients until the last patient was treated and followed up for 1 year.