Identifying Disparities in Autologous Hematopoietic Cell Transplantation (autoHCT) Utilization for Patients with Diffuse Large B-Cell Lymphoma (DLBCL) in California

Introduction: Relapsed/Refractory (R/R) DLBCL is an aggressive disease that is potentially curable with autoHCT or, more recently, chimeric antigen receptor (CAR) T-cell therapy. For patients who relapse, particularly after 12 months of initial therapy, autoHCT remains a standard of care treatment. Prior studies have found racial/ethnic disparities in the utilization of autoHCT in patients with lymphoma, with non-Hispanic Black/African American (Black) patients undergoing HCT less often than non-Hispanic White (White) counterparts, leading to inferior survival. Using a novel data linkage, we assessed autoHCT utilization patterns in the post-rituximab era and identified associations between sociodemographic factors and access to autoHCT.

Methods: This retrospective cohort study used linked data between the California Cancer Registry (CCR), the Center for International Blood and Marrow Transplant Research (CIBMTR) and the California Patient Discharge Database (PDD). From the CCR, we identified patients ages 18-79 diagnosed with DLBCL, between 2000 and 2016. R/R disease was identified in the PDD ≥6 months after DLBCL diagnosis using any of the following: 1) lymphoma ICD diagnosis code in the principal or second position, 2) metastatic recurrence ICD code in any position, or 3) chemotherapy ICD code in any position. Patients with second cancers before or within 1 year after R/R disease were excluded. Use of autoHCT was ascertained from CIBMTR and PDD. We estimated the cumulative incidence of autoHCT after R/R DLBCL diagnosis and determined the association of sociodemographic factors with receipt of autoHCT using multivariable Cox proportional hazards regression. All analyses accounted for death as a competing risk.

Results: Our cohort of 7,093 patients with R/R DLBCL were comprised of 57.2% Whites, 5.8% Blacks, 23.7% Hispanics, 12.3% Asians, and 0.4% Pacific Islanders. Overall, 19.5% of patients (n=1384) underwent autoHCT. Median time from DLBCL diagnosis to R/R disease was 12 months (Interquartile range (IQR)=7–28), and from DLBCL R/R diagnosis to autoHCT was 90 days (IQR 8–142 days). The cumulative incidence of autoHCT at 6 months after R/R disease diagnosis increased in recent time periods, from 14.9% during 2000-2005 to 18.7% during 2011-2016.

In the multivariable model, patients diagnosed with R/R disease in the most recent vs. earlier time periods were more likely to undergo an autoHCT (2011–2016 vs 2000–2005, Hazard Ratios (HR)=1.4, 95% Confidence Interval (CI): 1.22–1.59). Older patients had lower autoHCT utilization compared to younger patients aged <50 years: 50-59 (HR=0.83, CI: 0.73–0.95); 60-69 (HR=0.54, CI: 0.47–0.62); 70–79 (HR=0.10, CI: 0.08–0.14). In comparison to Whites, Hispanic patients were less likely to undergo an autoHCT (HR=0.87, CI: 0.75–1.0), but no differences were observed among other races/ethnicities. Additionally, patients residing a greater distance from a transplant center (>100 vs <30 miles) had lower autoHCT utilization (HR=0.64, CI: 0.50–0.83), as did those residing in low and middle (vs high) socioeconomic status neighborhoods (nSES) (HR= 0.73, CI: 0.63–0.83 and HR=0.81, CI: 0.70–0.93, respectively), patients with no (vs private) health insurance (HR=0.24, CI: 0.12–0.48) or with Medicaid or governmental insurance (HR=0.78, CI: 0.67–0.92), and those with 1-2 or ≥3 (vs no) comorbidities within 2 years of their R/R disease (HR=0.79, CI: 0.69-0.90; HR=0.39, CI: 0.34-0.45, respectively).

Conclusions: AutoHCT utilization in California has increased in more contemporary study years for patients with R/R DLBCL. However, disparities based on sociodemographic factors, race/ethnicity, and health insurance status remain evident. Geographical distance from transplant centers also affected transplant utilization. Mitigating these disparities is essential to ensuring equitable access to this potentially curative therapy, allowing better outcomes for all eligible patients. Given the recent changes in the treatment landscape for R/R DLBCL, this study may also serve as a foundation for future analyses of novel therapies in this population, including CD19 CAR T-cell therapy.