Inclusion Criteria:  Patient with newly diagnosed multiple myeloma; Patient not eligible for intensive treatment; Patient for whom first-line treatment with Lenalidomide-Dexamethasone will be initiated; Patient accepting the performance of an additional myelogram at the end of the 1st treatment cycle. Patient aged 18 years or older; Patient who has given free, informed and written consent; Patient affiliated to a social security scheme For women of childbearing age, use of effective contraception  Exclusion Criteria:  Patient with relapsed multiple myeloma; Patient eligible for intensive treatment; Patient for whom chemotherapy involves treatment other than Lenalidomide-Dexamethasone; Patient with a contraindication to lenalidomide treatment Pregnant or breastfeeding woman; Person subject to legal protection (safeguard of justice, curatorship,guardianship) or person deprived of liberty.