Patients With Newly Diagnosed Multiple Myeloma Comparing KTd vs. KRd Induction Therapy and Investigating a K-mono Maintenance Strategy

Inclusion Criteria: * Able to provide written informed consent in accordance with federal, local, and institutional guidelines * newly diagnosed, symptomatic multiple myeloma * Transplant-ineligibility: age \> 65 years or patients not eligible due to comorbidities determined by investigator or patients not willing to undergo autologous stem-cell transplantation (ASCT) on personal preference * Measurable disease, as defined by one or more of the following (assessed within 21 days prior to randomization): * Serum M-protein ≥ 0.5 g/dL, or * Urine M-protein ≥ 200 mg/24 hours, or * In subjects without detectable serum or urine M-protein, serum-free light chain (SFLC) \> 100 mg/L (involved light chain) and an abnormal κ/λ ratio * No prior treatment for multiple myeloma * Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0-1 * Patients at cardiac risk (NYHA \>II or pre-existing coronary heart disease or any other relevant cardiac complication) should be scheduled for a baseline echocardiography (ECHO) and can only be included if the left ventricular ejection fraction (LVEF) is ≥40%); independent of cardiac risk ECG has to be done for inclusion of Asian patients and patients \> 75 years of age * Adequate organ and bone marrow function within the 21 days prior to randomization defined by: * Bilirubin \< 2 times the upper limit of normal (ULN), Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 3 times the ULN * growth factor support fo…