MM-219 Smoldering Multiple Myeloma: A Demographic and Survival Analysis of a Retrospective Cohort Study in a University Hospital of Buenos Aires.

INTRODUCTION: Smoldering multiple myeloma (SMM) is a heterogeneous asymptomatic precursor to multiple myeloma (MM). It is the intermediate stage between monoclonal gammopathy of undetermined significance (MGUS) and MM, where there is a subset of patients with an indolent disease and a subset with progressive disease. The Mayo Clinic published a risk stratification model to help to differentiate these patients into 3 groups.

OBJECTIVE: To describe the demographic features of patients with SMM treated at the Italian Hospital of Buenos Aires.

MATERIALS AND METHODS: Retrospective cohort study, between 01/2005 and 05/2022. Consecutive patients with a confirmed diagnosis of SMM were included. Patients were followed from diagnosis until death, progression or loss to follow-up.

RESULTS: Thirty-nine patients with SMM were included, of whom 16 (41%) were men. The median age at diagnosis was 69 years (95% CI: 55-77). 25 (64%) had a previous MGUS; the median time to progression (TTP) from MGUS to SMM was 6.4 months. 19 (49%) of patients had progression to MM. Eight (20%) of patients died, 3 (37%) secondary to myeloma. The most common type of band was IgG kappa with 55%. The median of monoclonal band was 1.5 (CI: 1.2-2), the median of plasma cells in bone marrow biopsy was 15% (CI: 12-20), 29 patients (74.36%) presented evaluation of lytic lesions, 6 patients (15%) presented risk assessment by FISH, of which 2 were positive for del(17p). The median follow-up of the cohort was 92 months (95% CI: 72.4-127.2). The estimated median TTP for the entire cohort was 71 months (95% CI, 55-94). Eight (21%) patients presented a high risk of progression according to the Mayo clinic score. The median TTP according to the Mayo Clinic score was 44 months (CI: 27-62) for high-risk patients, 86.5 months (CI: 69-94) for intermediate-risk patients, and 75 months for low risk. Of the patients who presented del(17p) all progressed to myeloma during follow-up with a median TTP of 49 months (CI: 35-64). 1 patient entered the research protocol.

CONCLUSIONS: Our cohort demonstrated characteristics similar to those published. Patients with high-risk Mayo score and del(17p) by FISH showed faster progression, which emphasizes the need to include them in research protocols.