Impact of Bone Marrow Biopsy on Risk Stratification of Low-Risk IgG MGUS Patients

Introduction: Multiple myeloma (MM) is a plasma cell malignancy accounting for 10% of all hematological malignancies and characterized by significant inter and intra-patient heterogeneity. MM usually progresses from asymptomatic precursor stages, namely monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). Previous recommendation by the IMWG indicated that bone marrow evaluation should be deferred in patients with low levels of IgG M-protein ( Methods: A total of 244 patients with an IgG M-protein Results: Median age at diagnosis was 63 years and male to female ratio was 1.31. IgG k was present in 62.3%, while IgG l in 46.3% of patients. Median FLC ratio was 1.7 (IQR 0.9-3.2) and 51% of patients had an abnormal FLC ratio. In 54.5% of the patients, bone marrow infiltration by clonal plasma cells was ≥ 10%, reclassifying these patients as having SMM rather than MGUS. The time to progression to MM was significantly different between the patients with and without BM infiltration ≥ 10% in the Kaplan-Meier estimate (log-rank p = 0.004) (Figure 1). Subgroup analysis showed that patients with abnormal FLC ratio had a higher percentage of BM involvement (12% vs. 6%, p p = 0.002); M-spike was also higher in those with abnormal FLC ratio (0.9 vs. 0.6, p p = 0.015). Conclusion: Our findings indicate that over 50% of patients previously classified as low risk MGUS, based on the presence of an IgG monoclonal protein Disclosures Kastritis: Prothena: Honoraria; Janssen: Honoraria; Genesis pharma: Honoraria; Takeda: Honoraria; Amgen: Honoraria, Research Funding. Laubach: Novartis, Takeda, Celgene, Onyx: Research Funding; Novartis, Takeda, Celgene: Consultancy. Anderson: Bristol-Myers Squibb: Membership on an entity9s Board of Directors or advisory committees; MedImmune: Membership on an entity9s Board of Directors or advisory committees; Gilead Sciences: Membership on an entity9s Board of Directors or advisory committees; Oncopep: Other: scientific founder; Millenium Pharmaceuticals: Membership on an entity9s Board of Directors or advisory committees; C4 Therapeutics: Other: scientific founder. Richardson: Takeda: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Oncopeptides AB: Membership on an entity9s Board of Directors or advisory committees; Jazz Pharmaceuticals: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding. Dimopoulos: Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Onyx Pharmaceuticals, an Amgen subsidiary, Takeda Oncology: Consultancy, Honoraria, Other: Advisory Committee: Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Onyx Pharmaceuticals, an Amgen subsidiary, Takeda Oncology; Genesis Pharma: Research Funding; Novartis: Consultancy, Honoraria.