An interventional, non-randomised study to assess the risk of progression after discontinuation of maintenance therapy in sustained MRD negative complete remission by flow cytometry MM patients without high-risk features who have completed at least two years of maintenance therapy or who have discontinued maintenance due to side effects. The primary endpoint is to assess the rates of sustained MRD negativity by NGF in the bone marrow at 12 months after discontinuation of maintenance therapy.

Up to 70 patients over 18 years of age who have a diagnosis of Multiple Myeloma and have completed at least 2 years of maintenance therapy.

Participants would be divided in two groups: Group 1. Patients with detectable disease who have not achieved CR or VGPR as per IMWG criteria and/or detectable MRD and/or high risk features detectable disease, failed to achieve Complete Remission (CR) or Very Good Partial Remission (VGPR) continuing on maintenance therapy. Group 2. Patients who meet International Myeloma working Group (IMWG) criteria for very good partial response (VGPR) or complete response (CR). Patients who have achieved sustained MRD negative remission by next generation flow cytometry (NGF),defined by IMWG as MRD-negative at two time points that are at least 1 year apart, To the participants in this group will be offered to discontinue maintenance therapy, and it will be further divided in the following subgroups: Subgroup A) Patients who are willing to continue maintenance therapy. Subgroup B) Patients who are willing to discontinue maintenance therapy and continue monitoring. This subgroup will also include patients who have discontinued maintenance therapy earlier than 2 years due to side effects but also achieved sustained MRD negative CR might be also included.

The number of the study participants will be limited by the number of patients treated in Cork University Hospital who are meeting inclusion criteria.

Inclusion Criteria:

1. 18 years of age or over
2. Patient with diagnosis of multiple myeloma as per IMWC in first line of treatment (induction, consolidation, ASCT, maintenance is considered single line therapy for the purpose of this study, also discontinuation of 1 maintenance regimen due to toxicity and start of another is considered single line therapy for the purpose of this study).
3. Received at least 2 years of maintenance therapy, defined as any anti-myeloma therapy to prevent disease recurrence and prolong time in remission
4. Patients who have discontinued maintenance therapy earlier than 2 years due to side effects but also achieved sustained MRD negative CR might be also included
5. Patients must be able to understand and be willing to sign a voluntary informed consent form and agree to compliance with the protocol schedule, with the knowledge that they may withdraw consent at any time without impact on future medical care.

Exclusion Criteria:

1. Patients who have received more than one line of therapy (induction, consolidation, ASCT, maintenance is considered single line therapy for the purpose of this study, also discontinuation of 1 maintenance regimen due to toxicity and start of another is considered single line therapy for the purpose of this study) or patients who have not completer two years of maintenance therapy, unless maintenance was discontinued voluntarily and the patient has achieved sustainable MRD negative remission..
2. Patients with plasma cell disorders other than MM: lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia, AL amyloidosis, POEMS syndrome (Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal protein, and Skin changes), etc…
3. Prior organ transplant or condition requiring immunosuppressive therapy.
4. Prior allogenic haematopoietic cell transplant
5. Treatment with any investigational therapy that does not include maintenance as a part of the treatment strategy.
6. Unable to sign an informed consent form.