Fixed Duration vs Continuous Anti-CD38 Antibody Therapy Among Transplant Ineligible Older Adults With Newly-Diagnosed Multiple Myeloma

Inclusion Criteria: * Participants with newly diagnosed multiple myeloma that are transplant-ineligible * Measurable disease at the time of diagnosis, as defined by at least one of the following criteria: Serum monoclonal protein (M-protein) ≥ 5 g/L; Urine M-protein ≥ 200 mg/24 hours; Involved serum free light chain measurement ≥ 100 mg/L, provided serum FLC ration is abnormal; For IgA patients whose disease can only be reliably measured by serum quantitative immunoglobulin ≥ 750 mg/dL * Completed 18-20 cycles of daratumumab-lenalidomide-dexamethasone or isatuximab-lenalidomide-dexamethasone. * Obtained at least a partial response per the standard 2016 IMWG criteria * ECOG performance status 0-3 * Participant is able (i.e. sufficiently fluent) and willing to complete the quality of life and/or health utility questionnaires in English, French, or a provided validated language. * Participant consent must be appropriately obtained in accordance with applicable local and regulatory requirements. * Participants must be accessible for treatment and follow-up. * In accordance with CCTG policy, protocol treatment is to begin within 2 working days of participant enrollment. * Participants of childbearing potential must have agreed to use a highly effective contraceptive method. Exclusion Criteria: * Known history of concurrent amyloid light chain amyloidosis, POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes), and Waldenstrom's macroglobulinemia. * Patients receiving concurrent treatment with other anti-cancer therapy that would impact the ability to comply with protocol treatment are ineligible. Note: Participants with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of protocol treatment are eligible for this trial * Active, uncontrolled bacterial, fungal, or viral infection within 7 days prior to enrollment. * Known human immunodeficiency virus (HIV) with CD4 count \< 350 cells/microliter. Note that patients who are HIV positive are eligible, provided: * They are under treatment with antiretroviral therapy for at least 4 weeks prior to enrollment, with acceptable pharmacokinetic interactions and minimal overlapping toxicity with protocol therapy AND * HIV viral load must be \< 400 copies/ml within 16 weeks prior to enrollment AND * No history of opportunistic infections within the past year.