The Impact of Structural Racism and Social Determinants of Health on Fluorescence in Situ Hybridization Testing Among Patients with Multiple Myeloma

Introduction:Fluorescence in situ hybridization (FISH) testing to determine risk stratification is standard of care in multiple myeloma (MM). Specifically, FISH testing guides prognostication, treatment decision-making, and eligibility for biomarker-driven clinical trial participation. Structural racism and social deprivation have been linked to less access to biomarker testing; however, few studies have examined the impact of these factors on access to FISH testing among patients with MM. In this study, we examined the impact of structural racism and social determinants of health (SDOH) on FISH testing in patients with MM. Methods:This retrospective study used the nationwide Flatiron Health electronic health record-derived, de-identified database, focused on adult patients diagnosed with MM from January 1, 2011, to January 1, 2024 (follow-up through April 30, 2024). The primary outcome was a record of FISH testing within 60 days before or any time after a multiple myeloma diagnosis. Predictors included structural racism (based on neighborhood residential segregation), urbanicity (rural/urban), and area-level SDOH factors (including residence in medically underserved areas, vehicle ownership, and English proficiency). We estimated a series of multivariable Cox proportional hazards models to assess associations between each predictor and FISH testing, with adjustment for demographic and clinical factors (eg, age, sex, stage at diagnosis). Results: The cohort included 13,542 patients (6.6% Latinx, 2.0% Non-Latinx [NL]-Asian,18.0% NL-Black, 58.0% NL-White, and 16.1% Other/Unknown). Most patients lived in predominantly White neighborhoods (71.0%). Patients residing in neighborhoods with the highest percentage of households with limited English-speaking proficiency were less likely to have a FISH test than patients living in neighborhoods with the lowest percentage of households with limited English proficiency (adjusted Hazard Ratio [HR], 0.93; 95% CI, 0.87-0.99). There was a gradient relationship between vehicle ownership and FISH testing; ie, patients living in communities with the highest percentage of vehicle ownership had the highest rates of testing, with the likelihood of testing decreasing progressively across quartiles of decreasing vehicle ownership (Q2 HR: 0.94 [95% CI, 0.89-0.99], Q3 HR: 0.92 [95% CI: 0.87-0.98], Q4 HR: 0.90 [95% CI, 0.85-0.95]). There was no association between the presence of FISH testing and residential segregation, urbanicity, or residence in medically underserved areas. Conclusions: We observed lower rates of FISH testing among patients with MM living in neighborhoods with higher rates of limited English proficiency and lower rates of vehicle ownership. Findings from this study indicate that efforts aimed at addressing SDOH factors, particularly language and transportation barriers, should be prioritized to advance equity in FISH testing among patients with MM. Moreover, given the prerequisite of FISH testing in determining eligibility for biomarker-driven MM trials, findings from this study suggest potential opportunities for increasing equity in clinical trial participation through focus on the SDOH.