Background: Smoldering multiple myeloma (SMM) is an asymptomatic plasma cell disorder with the potential to progress to active multiple myeloma. We aimed to evaluate disparities in survival outcomes among patients with SMM based on race, income, gender, age, and socioeconomic status.

Methods: We conducted a retrospective analysis using the SEER 2017 database, including patients diagnosed with SMM between 2000 and 2022 (n=7,379). Patients diagnosed via autopsy, death certificate, or with incomplete survival data were excluded. Data on patient demographics (sex, race, median household income, and metropolitan status) and survival outcomes were collected. Descriptive statistics were used to summarize the population. Overall survival (OS) and cancer-specific survival (CSS) were evaluated using Kaplan-Meier analysis and Cox proportional hazards modeling. Statistical analysis was performed using SPSS, with p<0.05 considered significant. Adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated for all comparisons.

Results: Of the 7,379 patients, 55.3% were male and 44.7% female. The majority were White (70.5%) and aged 60–75 years (46.7%). Approximately 13.3% received chemotherapy, 60.8% were married, 89% resided in metropolitan areas, and 86.3% had a household income >$60,000.

The mean OS was 93.5 months (95% CI: 92.18–94.13), and varied significantly by race (p=0.002), income (p<0.001), and socioeconomic status (p<0.001). Median OS was 92.1 months for White, 95.1 months for Black, 102.4 months for Asian or Pacific Islander, and 79.4 months for American Indian/Alaska Native patients.

Patients with household incomes < $60,000 had a mean OS of 86.6 months, those with $60,000–$90,000 had 93.3 months, and those with >$90,000 had 97.0 months. Patients residing in metropolitan areas had a mean OS of 94.7 months compared to 83.7 months for those in non-metropolitan areas.

After adjustment, OS was significantly higher for patients with household income >$90,000 vs. <$60,000 (HR 0.78, 95% CI: 0.66–0.91, p=0.002) and for metropolitan vs. non-metropolitan residents (HR 0.82, 95% CI: 0.70–0.95, p=0.01).

CSS also varied significantly by race (p<0.001), income (p=0.005), and socioeconomic status (p<0.001). Mean CSS was 114.6 months for White patients, 121.3 months for Black patients, 119.0 months for Asian or Pacific Islander patients, and 98.4 months for American Indian/Alaska Native patients.

CSS was 112.9 months for patients with income <$60,000, 116.1 months for $60,000–$90,000, and 118.2 months for >$90,000. Metropolitan residents had a mean CSS of 117.1 months vs. 109.9 months for non-metropolitan. After adjustment, Black patients had significantly improved CSS compared to White patients (HR 0.69, 95% CI: 0.55–0.88, p=0.002), and those residing in metropolitan areas had improved CSS vs. non-metropolitan (HR 0.74, 95% CI: 0.57–0.96, p=0.022).

Conclusion: Our study reveals significant survival disparities in patients with SMM based on race, income, and geographic location. Black and Asian or Pacific Islander patients demonstrated better survival outcomes compared to White patients, while lower income and rural residence were associated with poorer outcomes. These findings underscore the critical need to address social determinants of health to ensure equitable care in smoldering multiple myeloma.

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2025
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