LAUSR

Smoldering multiple myeloma (SMM) is a precursor plasma cell disorder characterized by clonal proliferation without end-organ damage. Although asymptomatic, SMM remains clinically relevant due to its potential progression to multiple myeloma (MM) or AL amyloidosis. Recent studies suggest that early therapeutic intervention may delay progression in high-risk cases [1 – 4]. However, the real-world epidemiology of SMM — particularly cases diagnosed through routine clinical evaluation rather than screening — remains poorly characterized. Population-based screening, such as the iStopMM study, identi fi ed a 0.53% prevalence of SMM in individuals aged ≥ 40 years [5]. But these estimates may differ in clinical practice, where SMM is typically diagnosed incidentally during evaluation for other conditions. Prior studies using administrative databases have been limited by the absence of an ICD code to differentiate SMM from untreated or “ SLiM ” MM [6 – 8], making it dif fi cult to assess true population-level trends. We aimed to address this gap by describing the incidence and prevalence of clinically detected SMM between 2010 and 2022 using real-world data from a de fi ned Canadian health region. We conducted a retrospective cohort study using laboratory and clinical data from The Ottawa Hospital, the sole tertiary hematology center for Ontario ’ s Champlain Local Health Integration Network (LHIN). Due to the regionally centralized healthcare delivery and universal healthcare model in Ontario, all patients within the Champlain LHIN suspected to have a malignant hematologic disorder requiring a bone marrow biopsy — such as SMM — must be referred to our institution. In contrast, MGUS may be diagnosed and monitored by community hematologists or internists and would not necessarily be captured in our dataset. We identi fi ed all adults tested for monoclonal proteins (serum protein electrophoresis [SPEP], urine protein electrophoresis