Abstract 2628: Racial differences in the impact of socioeconomic status on cancer-specific survival in multiple myeloma
Authors: Deng Huiwen , Zolekar Ashwini , Huang Hsiao-Ching , Smart Mary H. , Hubbard Colin C. , Chiu Brian C. , Patel Pritesh R. , Sweiss Karen , Calip Gregory S. 
Published: July 2021

Abstract
Background: Multiple myeloma (MM) incidence and outcomes differ across racial/ethnic groups in the United States. Interactions between socioeconomic status (SES) with ethnicity in MM incidence and survival outcomes are not well understood. Our objective was to evaluate disparities in cancer-specific survival of patients diagnosed with MM by race/ethnicity.
Methods: We conducted a population-based retrospective cohort study of patients ages 20+ years diagnosed with MM between 2000 and 2015 using Surveillance, Epidemiology and End Results, Census Tract-level SES and Rurality Database. SES was defined using the National Cancer Institute's time-dependent composite score developed by Yost et al. (2001). Yost index quintiles were where the 1st and 5th quintiles representing the lowest and highest SES categories respectively. Cumulative incidence functions were used to analyze cancer-specific survival across strata racial/ethnic and SES and equality of functions was determined using Gray's test. Subdistribution hazard ratios (SHR) and 95% confidence intervals (CI) were calculated using the Fine and Gray regression models adjusted for age, sex, year of diagnosis, marital status, insurance status, and treatment with chemotherapy. Race-specific risk estimates were stratified by age (&lt;65 and 65+ years).
Results: Overall, 58,095 MM patients were included in our analysis among whom 63.0% were non-Hispanic White, 19.5% were Black, 0.3% were American Indian/Alaskan Native, 5.8% were Asian/Pacific Islander and 11.4% were Hispanic. Compared to White MM patients (median age 69 years), Black (64 years), American Indian/Alaskan Native (64 years), Asian/Pacific Islander (67 years) and Hispanic (64 years) patients were younger on average. A higher proportion of Black (42.8%) and Hispanic (27.9%) MM patients were in the lowest SES quintile compared to White (10.6%), American Indian/Alaskan Native (15.2%), and Asian/Pacific Islander (8.9%) MM patients. Cumulative incidence functions for cancer-specific survival were significantly different across SES quintiles (P &lt; 0.0001) and racial/ethnic groups (P &lt; 0.0001). Overall, MM patients in the lowest SES quintile had a significantly increased risk of MM-specific mortality (SHR: 1.28, 95% CI 1.21-1.36) compared to patients in the highest quintile. Risk estimates comparing the lowest to the highest quintile of SES were higher among Black (SHR 1.39, 95% CI 1.08-1.77), Hispanic (SHR: 1.78, 95% CI 1.21-2.63), and White (SHR 1.44, 95% CI 1.23-1.69) MM patients ages &lt;65 years at diagnosis.
Conclusion: Low SES level is independently associated with poor MM-specific survival. However, the impacts of SES on MM-specific survival differ by race/ethnicity and age with the greatest increased risk observed in younger Black, Hispanic, and White patients.
Citation Format: Huiwen Deng, Ashwini Zolekar, Hsiao-Ching Huang, Mary H. Smart, Colin C. Hubbard, Brian C. Chiu, Pritesh R. Patel, Karen Sweiss, Gregory S. Calip. Racial differences in the impact of socioeconomic status on cancer-specific survival in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2628.