Examining Racial Disparities in Diffuse Large B-Cell Lymphoma (DLBCL) Outcomes within the Veterans Health Administration (VHA)

INTRODUCTION:

The incidence of DLBCL in the United Sates is projected to increase to 32, 443 new cases per year by 2025. With increasing incidence and prevalence, DLBCL prognosis has improved significantly in the past decade through the addition of novel therapies such as new monoclonal antibodies, chimeric antigen receptor T-cell (CAR-T) therapy, antibody-drug conjugates, and most recently bispecific T-cell engagers. Despite these improvements, racial and ethnic disparities continue to impact outcomes in DLBCL patients (Flowers 2012). The purpose of this study was to assess racial and ethnic differences in DLBCL patients and outcomes within the VHA, an equal access system where confounding factors such as disease biology and socioeconomic status are more controlled giving us an opportunity to examine racial disparities. The aim of this study is to present a final analysis the final analysis of racial and ethnic differences in DLBCL patients within the VHA over a time span of 11 years.

METHODS:

Trained abstractors performed a retrospective chart review of 6266 randomly selected DLBCL patients treated in the VHA nationwide between 1/1/2011 and 12/31/2021. Patients diagnosed with DLBCL were included. Patients were excluded if they had a diagnosis other than DLBCL, had incomplete records, or were diagnosed and treated outside the VHA. Data was collected on baseline patient demographics, disease characteristics, and treatment. Survival time was determined via electronic health record query on 1/4/2023. The study population was divided into non-Hispanic Black (NHB), non-Hispanic White (NHW), Hispanic (H), and other. Chi-squared tests were used to analyze the relationship between race and variables of interest.

RESULTS:

3178 patients met inclusion criteria for analysis. Patients were predominantly male with a median age of 69 and presented primarily with advanced disease (Baseline Characteristics-Table 1). NHB were diagnosed at a younger median age (63 years) when compared to the NHW, H and other (69 years, P < 0.001). Patients in each subgroup presented with similar rates of stage I/II and III/IV disease with no statistically significant difference in stage at presentation amongst each racial subgroup (P=0.61).

Of all the patients who received chemotherapy, the objective response (OR) rate was 79.2% with a complete response (CR) rate of 66.4%. The response rates were similar across the 4 subgroups with most patients achieving a CR after first-line therapy (P=0.74). There were no statistically significant differences in OR rates amongst subgroups (P = 0.95).

Median overall survival (mOS) for the entire population was 69.6 months (95% CI = 65-75), with a mOS of 85.1 months (67-112), 85.9 months (60-112), 67.4 months (60-73), and 71.2 months (49-122) for NHB, H, NHW, and other patients respectively (Figure 1). There was no statistically significant difference in mOS amongst subgroups (P = 0.13). The 1-year, 3-year, and 5-year survival rates were also similar between subgroups (P=0.97, P= 0.39, P=0.32 respectively).

CONCLUSION:

This study represents one of the largest retrospective analyses of DLBCL in the VHA nationwide, highlighting that there is no statistically significant racial difference in DLBCL outcomes for patients treated within the VHA. Our study highlights the significance of equal access system and that disease biology and other social factors can be mitigated resulting in equal response to treatment and OS amongst all groups.

Potential limitations of this study include using retrospective data on a predominantly white, male population that may not truly represent general DLBCL population data. The study period is mainly until 2021 with limited data on the accessibility of newer, novel treatments.

With the development of newer, expensive treatments, especially Bispecific T Cell Engagers and CAR-T therapy, it is imperative to study utilizations of these novel treatments and study racial differences in this new treatment non-chemotherapy-based era.