Monitoring of Deep of Response During Lenalidomide Maintenance in MM Patients Achieving at Least Very Good Partial Response (MRD)

Inclusion Criteria: * Patient is, in the investigator(s) opinion, willing and able to comply with the protocol requirements. * Patient has given voluntary written informed consent before performance of any study-related procedure not part of normal medical care, with the understanding that consent may be withdrawn by the patient at any time without prejudice to their future medical care. * Patient has achieved at least a Very Good Partial Response (VGPR) before starting maintenance therapy * Availability of a bone marrow sample at diagnosis stored in the Institution tissue bank to create patient-specific probes derived from IgH rearrangement * Patients must receive Lenalidomide-based regimen as maintenance after a first line therapeutic approach * Patient is 18 years old at the time of signing the informed consent * Patient has a Karnofsky performance status ≥ 60%. * Patient has a life-expectancy \> 6 months * Patient has HBV, HCV and HIV negative test. * Patients must have normal ECG and NYHA ≤ 2; an evaluation of ejection fraction by ECHO or MUGA is optional * Patients must be informed on acute and late toxicity of Lenalidomide treatment and must sign an informed consent. Exclusion Criteria: * Any serious medical condition, including the presence of laboratory abnormalities, which places the subject at an unacceptable risk if he or she participates in this study or confounds the experimental ability to interpret data from the study. * Achieving of a PR or less before starting maintenance therapy * Pregnant or lactating women. A serum β-hCG pregnancy test must be performed at the Screening visit, for female patients of child-bearing potential. If the test is positive, the patient must be excluded from the study. Confirmation that the patient is not pregnant must be established by a negative serum or urinary pregnancy test with the result obtained 1 day prior to the Baseline visit (or the day of the visit if results are available before drug delivery). A pregnancy test is not required for naturally post-menopausal women (who have not had menses at any time in the preceding 24 consecutive months) or surgically sterilised women (hysterectomy, bilateral ovariectomy, bilateral salpingectomy).