S1803, Lenalidomide +/- Daratumumab/rHuPh20 as Post-ASCT Maintenance for MM w/MRD to Direct Therapy Duration

Patients are enrolled to screening (Reg Step 1) prior to or after ASCT but prior to Reg Step 2. Patients are followed until they will begin Maintenance and then registered to Reg Step 2 (first randomization). Patients are randomized between Lenalidomide for 2 years and Lenalidomide + Daratumumab/rHuPH20. After 2 years of Maintenance, MRD is assessed to guide further therapy. MRD-positive patients will continue with the assigned treatment. MRD-negative patients will be further randomized (Reg Step 3) to either continue or discontinue the assigned treatment. Patients are treated for up to 7 years from Step 2 reg and followed for up to 15 years.

Registration Step 1 Except where otherwise indicated below that test is required in a shorter timeframe, all tests for establishing baseline disease status must be completed within 60 days prior to registration. All test results must be documented on the Baseline Tumor Assessment Form for Multiple Myeloma and the Onstudy Form. Inclusion Criteria * Patients must have had a confirmed diagnosis of symptomatic multiple myeloma (See Section 4.1) that required systemic induction therapy prior to autologous stem cell transplantation (ASCT). * Patients with disease measurable by serum light chain assay alone are eligible (defined as \>/= 100 mg/L on involved light chain). * Patients must be registered to Step 1 prior to registration to Step 2. Registration to Step 1 may take place prior to or after autologous stem cell transplant (ASCT), but after completion of induction therapy. * Patients must have initiated induction therapy within 12 months prior to registration Step 1 and have received at least two cycles of induction therapy. * Patients must be willing and able to take DVT prophylaxis (aspirin, low molecular weight heparin, warfarin, or equivalent oral anticoagulation). * Patients must be \>/= 18 and \