QUIREDEX: Revlimid (Lenalidomide) and Dexamethasone (ReDex) Treatment Versus Observation in Patients With Smoldering Multiple Myeloma With High Risk of Progression

Inclusion Criteria: * Must be able to comply with the protocol requirements * Must voluntary sign the informed consent before performance of any study-related procedure not part of normal medical care * Age ≥ 18 years * Patient recently diagnosed with smoldering Multiple Myeloma with high risk of progression to symptomatic Multiple Myeloma defined as follows: * Bone Marrow infiltration ≥ 10% CPs and M component Ig G ≥ 3 g/dl or Ig A ≥ 2 g/dl or Bence Jones Protein \> 1 g/dl and absence of: hollowed out areas of bone, Hypercalcemia (Calcium-serum \< 11.5 mg/dl), Renal Failure (creatinine \< 2 mg/dl) and anaemia (Hb \> 10 g/dl or at least 2g/dl under normal value. * Alternatively, patients with Bone Marrow infiltration with CPs ≥ 10 %, or Ig G ≥ 3 g/dl or Ig A ≥ 2 g/dl or Bence Jones Protein \> 1 g/24h (but not the two of them together) and always without: lytic lesions, Hypercalcaemia, Renal Failure and Anaemia could be admitted with the following additional criteria: * % CPs abnormal (CPa/CpcMO) ≥ 95 % with immunodeficiency, defined as diminution of levels of one or two Immunoglobulins of more than 25% respect normal values. * ECOG \>= 2. * The patient has to be able to complain with the protocol visits. * Women of childbearing age must have a negative pregnancy test during the 14 days before first dose. And they must accept to use anticonceptive methods beginning during all the study until 4 weeks after the last one. Exclusion Criteria: * Any other organic or mental illness that could make impossible to sign the Inform consent. * Patients previously received treatment to smoldering Multiple Myeloma. * Pregnancy or breast-feed women * Hollowed out areas of bone, anaemia, renal failure and Hypercalcemia * The following laboratory data: * Absolute neutrophil count ≥ 1000/mm3 * Platelet count ≥ 75000/mm3 * Aspartate transaminase (AST) or Alanine transaminase (ALT ) ≤ 3 x the upper limit of normal. * Total bilirubin: ≤ 2 x the upper limit of normal. * Patients with \>= Grade 2 peripheral neuropathy within 14 days before enrolment. * Patient with a previous clinical history of another malignant illness except for squamous cell carcinoma or skin cancer or cervical cancer except the patient could be free of symptoms during ≥ 5 years. * Patient has hypersensitivity or adverse events previous to lenalidomide or Dexamethasone. * Patient who has major surgery during the 4th weeks previous inclusion. * Patient has received other investigational drugs within 30 days before enrolment.