Smoldering Multiple Myeloma in Latin America- Risk Stratification

Introduction: Smoldering multiple myeloma (sMM) is a heterogeneous clinical entity that behaves as an indolent or aggressive plasma cell disease that can evolve to symptomatic MM. There is scarce data about sMM in Latin America (LA) and we aimed to characterize sMM in this region.

Methods: The Brazilian and Latin America Myeloma Study Groups (GBRAM and GELAMM) established a consortium to conduct a retrospective cohort study of sMM cases diagnosed from 2015 to 2023. Demographics and diagnostic and prognostic tools data were collected. We also evaluated risk factors associated with the chance of progression to MM using the 20-2-20 risk stratification criteria. Each number represents a factor, i. e., 20% or more of plasma cells in the bone marrow, 2g/dL of the M component and a free light chain ratio of 20. No factors, the presence of one and > two factors were considered low, intermediate or high-risk, respectively. The progression-free survival (PFS) and overall survival (OS) were calculated.

Results: A total of 247 pts, from 35 different institutions in eight different countries, were included. The median follow-up was 42.2 months. The median age at diagnosis was 64 (34 - 90) yrs and 158 (64%) patients were female. The immunoglobulin isotypes IgG and IgA and light chains were identified in 158 (64%), 70 (28.3%) and 14 (5.7%), respectively. A total of 210 (85%) pts had FLC analysis, 111 (44.9%) pts had a total body MRI or PET-CT and 106 (42.9%) pts had low-radiation total body CT. A total of 191 (77.3%) pts had all the 20-2-20 criteria available, 74 (38.7%) of whom were low risk, 61 (32.9%), intermediate risk and 56 (29.3%), high-risk. Of the total number of patients included, 59 (23.9%) progressed and 42 of these had all the 20-2-20 criteria. Ten (23.8%), 14 (33.3%) and 18 (42.8%) patients were low, intermediate and high risk, respectively, based on the 20-2-20 criteria. The median time to progression was 34 (3 - 111) months and 11 patients had progressed over the 12 months from diagnosis. The chance of progression, considering the 20-2-20 criteria risk factors, was identified, but was not significant in the whole group (p = 0.08). However, the comparison between the low- (0) and high-risk (2-3) groups demonstrated statistical significance (p = 0.04). Thirteen (5%) pts died or were lost to the follow-up.

Discussion-Conclusion

This study is the first and largest sMM patient cohort representation in LA. Despite the fact that 40% of the sMM in this study belonged to the public health system sector, where the accessibility to diagnosis tools is limited, most of the patients underwent specific imaging, FLC assay and bone marrow studies, allowing us to correctly identify and confirm cases of sMM in our region. With the 20-2-20 model, we could discriminate between low- and high-risk classification prognoses. More patients with access to all the needed tests and a longer follow-up could consolidate this score in our population.