In the Netherlands, the standard treatment for multiple myeloma is a combination of different medicines named daratumumab-lenalidomide-dexamethasone, abbreviated as Dara-Rd. In many patients this treatment results in suppressing the disease for a long time. The treatment is continued until it is not effective anymore and the disease progresses.

But until now it is unknown whether continuous therapy also leads to prolonging life. In addition, there are concerns about side effects, leading to a reduced quality of life, the development of severe toxicity that remains, which hampers subsequent therapy, and high costs due to prolonged treatment.

There are indications that temporarily stopping treatment is safe, leading to fewer side effects and allows recovering from toxicity or damage due to treatment. This may improve the quality of life.

Inclusion Criteria:

• Patient was diagnosed with MM, based on the IMWG criteria, and measurable disease at the time of diagnosis (appendix A).
• Age ≥ 18 years.
• Patient was treated with 12 cycles (13 cycles is accepted) of Dara-Rd and will continue treatment with Dara-Rd. Reduced dosing of lenalidomide, but not to less than 5 mg, and previous discontinuation or dose reduction of dexamethasone is allowed.
• Partial response or better after treatment with 12 cycles of Dara-Rd, without signs of biochemical progression.
• ANC ≥ 1.0x109/L and platelets ≥ 75x109/L.
• Patient is capable of giving informed consent.
• Written informed consent.

Exclusion Criteria:

• Patient with non-secretory MM at diagnosis of the disease, i.e., before the start of treatment with Dara-Rd.
• Patient in whom a plasmacytoma was the only measurable parameter at diagnosis of the disease, i.e., before the start of treatment with Dara-Rd.
• Patient in whom urine M-protein was the only measurable parameter at diagnosis of the disease, i.e., before the start of treatment with Dara-Rd.
• Patient in whom treatment with daratumumab, lenalidomide or both has been discontinued for whatever reason (patients may only have discontinued dexamethasone).
• Patient in whom continuation of treatment with Dara-Rd is deemed not feasible because of medical reasons.
• Any psychological, familial, sociological and geographical condition potentially hampering compliance with the study protocol and follow-up schedule.