Secondary Objectives: 1) To evaluate the prevalence of non-adherence to lenalidomide in MM patients, and independent risk factors thereof. 2) To validate the utility of questionnaires assessing adherence in identifying MM patients at risk for lenalidomide non-adherence.3) To assess the association between non-adherence to lenalidomide and long-term response, measured as time to progression (TTP) at 18 months.