Smoldering multiple myeloma (SMM) is an asymptomatic clonal plasma cell disorder with a prevalence of 0.5% in the > 40 yrs population. Effort has been made to characterize these patients in the real world. There is scarce data about SMM in Latin America (LA) and we aimed to characterize SMM in this region.

A consortium between the Brazilian and Latin America myeloma study groups (GBRAM-GELAMM) were stablished to conduct a retrospective cohort study of SMM cases diagnosed from 2015 to 2023. Data collected included demographics, diagnostic and prognostic tools. We also captured data of progression to MM and SMM management. Progression-free survival (PFS) and overall survival (OS) were calculated.

A total of 247 pts had been included, from 35 different institutions belonging to eight different countries. Ninety-five (38.5%) of pts were followed in the public health sector (PS). The median age at diagnosis was 64 (34-90) yrs and 158 (64%) patients were female. The immunoglobulin isotype were IgG, IgA and light chains in 158 (64%), 70 (28.3%) and 14 (5.7%), respectively. Regarding exams availability, 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 from whom 74 (38.7) were low risk, 61 (32.9%) were intermediate risk, 56 (29.3) were higk risk. From the total of patients included 59 (23.9%) progressed, from whom 10 (4%), 14 (5,7%),18 (7.3%) and 17 (28.9%) were low, intermediate, high risk and unknow data, respectively. Median time to progression was 34 (3-136) months, and 11 patients had progressed over 12 months from diagnosis. Chance to progression considering the risk factors from 20-2-20 criteria was identified but not significant (p = 0.08). Thirteen (5%) pts died or lost follow-up. The median follow-up was 42.2 months.

This is the first cohort with representation of patients with SMM in LA. Although the majority of MM patients in LA are followed in the public sector, only 40% of the SMM cases in the present study belong to this sector, reveling the access difficult to diagnosis tools for SMM cases in the public sector. The majority of pts did have access to CT, MRI, PET, FLC assay and bone marrow study, which we interpret as a correct identification of SMM criteria in our cases. The 20-2-20 criteria works for the study population stratification although no statistical difference was observed, possibly due to the number of cases and/or shot follow-up.