Abstract
INTRODUCTION: Smoldering multiple myeloma (SMM) is a precursor condition to active multiple myeloma (MM). While surveillance is standard, data on its effectiveness in preventing irreversible complications is limited. METHODS: We conducted a two-center matched retrospective cohort study comparing 57 patients who progressed from SMM (pSMM) with 57 de novo MM (dnMM) patients, matched by age and diagnosis year. Primary endpoints were end-organ damage and progression-free survival (PFS). RESULTS: Median surveillance prior to progression in pSMM was 40 months. At active MM diagnosis, irreversible renal/bone complications were observed in 44% of pSMM patients compared with 72% of dnMM (p = 0.002). dnMM patients presented more frequently with hypercalcemia (12.3% vs. 1.8%, p = 0.03), lytic lesions (67% vs. 45%, p = 0.02), pathological fractures (31% vs. 10%, p = 0.008), and detrimental bone disease (58% vs. 25%, p < 0.001). ISS and R-ISS stages were higher in dnMM, while treatment patterns were similar. At 3 years, PFS was significantly higher in pSMM (59% vs. 30%, p = 0.01), as was overall survival (OS; 92% vs. 76%, p = 0.01). Clinical surveillance was associated with reduced disease burden, fewer irreversible complications, and improved PFS and OS compared with dnMM. CONCLUSION: These findings support surveillance effectiveness and highlight the need to optimize follow-up strategies.