Investigating Differences in Clinical Outcomes Among Patients (Pts) Diagnosed with Multiple Myeloma (MM) Across Racial Groups

Introduction: MM is the most common hematologic malignancy diagnosed in Black/African American (AA) pts. AA pts are 2- to 3-times more likely to be diagnosed with MM than White (W) pts despite clinical trials enrolling a majority of W pts. Even with disparities in access to frontline treatment (Tx) for AA pts, multiple studies have indicated a comparable, if not longer, overall survival (OS) in AA pts when compared with W pts. When evaluated in an equal access setting, 2 large population-based studies have corroborated this finding, suggesting a potential effect modification associated with AA pts with MM, such as younger median age at diagnosis and lower incidence of high-risk cytogenetics. Our study aims to further characterize racial disparities in Tx and survival of MM pts, and to identify potential factors that may act as effect modifiers on survival.

Methods: This was a retrospective observational study using Flatiron Health, a US-based real-world clinical database collected from electronic health records and comprising ~80% pts from community practices and ~20% from academic centers. Inclusion criteria were: age ≥ 18 y; documented MM diagnosis (index date) between 1 Jan 2011 to 31 Oct 2021; received at least first-line (1L) systemic Tx for MM; and ≥ 3 mo of follow-up. Data analyzed included demographics, clinical characteristics, genetic testing, high-risk cytogenetics, Tx characteristics, progression-free survival (PFS), and OS. Descriptive statistics were used for all continuous, categorical, and binary study variables. PFS and OS were calculated from index date to disease progression or death, respectively, using the Kaplan-Meier method with censoring at the end of follow-up. Multivariate Cox proportional hazard regression models were used to assess the association between racial groups and risk for death, while adjusting for confounders of interest.

Results: Of 9083 pts analyzed, 65%, 20%, and 15% were W, AA, and 'Other race' (O), respectively. Median age at diagnosis was 69 y, with AA pts being slightly younger at diagnosis (66 y), compared with W (70 y), and O (68 y) pts. Slightly more AA pts were female (54%) compared with W (43%) and O (47%) pts. Of the 68% of pts tested for high-risk cytogenetics, defined as the presence of del(17p), t(4;14) or t(14;16), a total of 19% of W, 17% of AA, and 18% of O pts were positive. When +1q and karyotyping for hypodiploidy and del(13q) were included, 36% of W, 35% of AA, and 37% of O pts were positive. Of pts with recorded International Staging System results (54%), 19% of W, 18% of AA, and 18% of O pts had Stage III disease. Median PFS in the overall cohort was 38.5 mo, with similar PFS seen among W (37.5 mo), AA (40.2 mo), and O (40.6 mo) pts (Figure 1A). Overall, 42% of pts in the cohort were deceased. Death was recorded in 44%, 40%, and 37% of W, AA, and O pts, respectively. Median OS from diagnosis for the overall cohort was 66.6 mo. This was shown to be significant by race (P = 0.0008), with W, AA, and O pts having a median OS of 63.6 mo, 74.5 mo, and 72.6 mo, respectively (Figure 1B). Multivariate Cox proportional hazard models showed that AA and O pts had a lower risk of death compared with W pts (hazard ratios [HR] 0.88 and 0.86, respectively). Pts with MM aged < 65 y also had lower risk of death (HR 0.73). Other clinically relevant factors associated with lower risk of death include stronger functional status (Eastern Cooperative Oncology Groups score 0-1, HR 0.55) and receipt of stem cell transplant (HR 0.34) per the multivariate Cox proportional hazard models. Factors associated with higher risk of death include high-risk cytogenetics (HR 1.52) and having a Charlson Comorbidity Index (CCI) score ≥ 1 (HR 1.15).

Conclusion: This study confirms previously observed findings of longer PFS and OS not only in AA pts diagnosed with MM, but also in other non-W races (O). These pts had similar PFS to 1L therapy due to Tx access. These findings were captured in a relatively equal-access setting where all pts received at least 1L Tx, suggesting that other potential factors act as effect modifiers on survival. Protective factors against death include younger age and stronger functional status at diagnosis. Risk factors that increased the likelihood of death included presence of high-risk cytogenetics and higher CCI scores. This analysis underscores the value and impact of equal access to care for the improvement of health outcomes, specifically in relation to minority pt populations in the US.

Saunders:BMS: Current Employment, Current equity holder in publicly-traded company. Slaff:Merck (Spouse): Current Employment; Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Subbiah:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Gu:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Rosenberg:Takeda: Other: Institutional Research; Kangpu: Other: Institutional Research; Bristol Myers Squib: Research Funding; Adaptive: Consultancy; Janssen, Takeda: Speakers Bureau.