This protocol is an international, multicenter, comparative, open and randomized study designed to compare the safety and efficacy (in terms of response rate) from three induction chemotherapy schemes -Thalidomide/Cyclophosphamide/Dexamethasone versus Thalidomide/Dexamethasone versus Thalidomide/Melphalan/Prednisone. Finally, this study is also designed to compare the safety and efficacy (in terms of duration of response) of two maintenance chemotherapy regimens - Thalidomide/Prednisone versus Thalidomide. Each treatment arm will include 100 patients and assessments and scheduled visits will be conducted in three periods: Pre-treatment, treatment and monitoring. Security will be evaluated by monitoring all adverse events, physical examination, vital signs and biochemical studies. Response to treatment will be evaluated according to the EBMT21 criteria and will be assessed on day 1 of each cycle of induction, at the end of nine cycles of induction therapy and monthly during the first year of maintenance therapy and every 3 months thereafter.