No Survival Disparity between Black and White Patient's with Stage I/II Diffuse Large B-Cell Lymphoma and It's Significance

Background

Diffuse large B Cell Lymphoma (DLBCL) is the most common subtype of non-Hodgkin Lymphoma. Limited stage I/II DLBCL has an excellent prognosis with five-year overall survival (OS) of at least 70%. Black patients with DLBCL stage I-IV collectively are reported to have worse outcomes on multivariate analysis. There is scant data to evaluate the disparity between Black and White patients in limited-stage DLBCL. We aimed to determine the characteristics and outcomes for stage I/II DLBCL between Black and White patients using the National Cancer Database (NCDB) from 2004 to 2017.

Methods

Chi-square and Wilcoxon rank sum tests were performed to assess the differences in characteristic variables between Black and White patients with limited-stage DLBCL. Multivariate Cox regression analysis was conducted to identify the independent determinants affecting outcomes in stage I/II DLBCL. Fifteen variables in the analysis include demographics (age, sex, race, ethnicity), social (distance traveled, facility type, insurance status, median household income, education level), clinical features (B symptoms, HIV status, Charlson-Deyo score), management (year of diagnosis, stage, treatment type). Kaplan-Meier (KM) survival curves were used to evaluate survival between Black and White patients with stage I / II DLBCL. Additionally, exact matching for all characteristic variables between Black and White patients were performed to compare survival using the Cox model with robust variance estimators.

Results:

For stage I/II DLBCL, KM survival rate estimates at 1-year, 3-year, and 5-year were 78.8%, 68.8%, and 62.1%, respectively. Diagnosis after 2004 measured in 4 intervals did not impact outcome after rituximab approval in 1997. There is no statistical survival difference (p = 0.5263) in stage I/II DLBCL between Black and White patients. Age > 60 years, males, higher Charlson score, more B symptoms, and positive HIV status were independent variables that affected survival (above not shown). In limited-stage DLBCL, Black patients were younger, had higher Charlson scores, more B symptoms, and higher percent were HIV positive(Table 1). Exact matching of paired samples between Black and White patients for all variables using the Cox model with robust variance estimators similarly showed no statistical difference in survival (p=0.1818). Interestingly, Hispanic patients (HR=0.84) have better survival than non-Hispanic patients (Table 2).

Conclusion:

Black patients have reported worse survival for stages I-IV DLBCL collectively. However, there is no statistically significant survival difference in stages I-II. Our study's independent characteristics associated with worse outcome are similar to DLBCL stage I-IV studies except for race. Yet the observed disparities between Black and White patients with stage I/II DLBCL do not appear to impact survival as an outcome. The exact matching of variables, including demographic and social determinants, confirmed survival remained similar, not better. Therefore, in early-stage DLBCL, the biology of DLBCL may be more predictive of outcome for race. Determinants of outcome should be stratified by stage. Advanced DLBCL remains an independent prognostic feature. Achieving health equity in DLBCL may be more impactful on advanced stage than for limited stage, as there is no survival disparity between Black and White patients in stage I/II DLBCL despite the disparity in demographic and social determinants.