Racial and Ethnic Disparities in Systemic AL Amyloidosis: Examining Differences in Clinical Presentation and Outcomes

Background: Racial/ethnic minorities have been underrepresented in most population-based studies of AL amyloidosis published to date. This observation stands in marked contrast to multiple myeloma, a closely related disorder with a twofold higher incidence among blacks vs. whites. Given the scarcity of information about health disparities in AL amyloidosis, we aimed to characterize the clinical presentation and outcomes of this unique plasma cell disorder according to race/ethnicity. Methods: Data on consented patients with systemic AL amyloidosis seen at the Boston University Amyloidosis Center between 1990 and 2020 were obtained from a prospectively maintained database (ClinicalTrials.gov Identifier: NCT00898235). Sociodemographic factors, hematologic and organ disease markers, along with the use of high-dose melphalan and stem cell transplantation (HDM/SCT) were stratified by self-reported race/ethnicity. Groups included non-Hispanic white (NHW), non-Hispanic black (NHB), Hispanic, and non-Hispanic other (NHO). Differences were assessed by χ2 test for categorical variables and one-way ANOVA test for continuous variables. Multivariable logistic regression was used to determine the influence of variables on HDM/SCT utilization. The effect of race/ethnicity on mortality was estimated by multivariate Cox proportional hazards regression with adjustment for relevant confounders. Results: In a cohort of 2,416 patients, only 14% were underrepresented minorities (Figure 1A). At diagnosis, racial/ethnic minority groups were younger than NHWs by a median of 4-6 years. NHBs comprised 8% of the cohort and had higher-risk sociodemographic factors (e.g. educational attainment of high school level or less among 39% vs. 25% for NHWs; P < .001). Furthermore, there was an indication of more aggressive disease among NHBs with more patients having a difference between involved and uninvolved free light chains (dFLC) of > 180 mg/L (39% vs. 22-33%; P = .044). Hispanics comprised 4% of the cohort and presented with more advanced cardiac disease (i.e. median BNP of 1,041 pg/mL vs. 221-480 pg/mL; P = .001). Among a subcohort of 1,668 patients with available treatment data, 33% of Hispanics and 39% of NHBs were treated with HDM/SCT as compared to 47% of NHWs (P = .071). This treatment disparity was accounted for by sociodemographic (i.e. lower educational level) and physiologic risk factors (i.e. stage III cardiac involvement), rather than race/ethnicity itself. At data cutoff in