Racial Differences in the Presentation and Outcomes of Diffuse Large B-Cell Lymphoma in the United States.

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL), and can often be cured with standard chemoimmunotherapy, but there is great heterogeneity in patient outcomes.

To examine the baseline characteristics and outcomes in a national cohort of patients(pts) with DLBCL we performed a retrospective cohort analysis of DLBCL cases diagnosed from 1992 to 2005 in 13 Surveillance, Epidemiology and End Results (SEER) registries. International Classification of Diseases for Oncology histology codes 9680, 9684, 9697 were used to identify cases. Cases with known race were grouped into White (W), Black (B), and others (O; Asians or Pacific Islanders, and American Indians or Alaska Natives). Subtype-specific DLBCL incidence rates were calculated for population subgroups according to age, sex, race, registry and time period, expressed as new cases per 100,000 population and age-adjusted to the 2000 US standard population. Incidence rates were compared by sex and by race by computing incidence rate ratios (IRR) and 95% Confidence Intervals (95% CI). Two- and 5-year relative survival rates (RSR) were calculated by actuarial methods.

Between 1992 and 2005, 34,436 cases of DLBCL were recorded in SEER. Over this period, the incidence of imunoblastic DLBCL decreased from 1.7 to 0.1 cases per 100,000 population while the incidence of DLBCL as a whole remained stable. Incidence rates were higher among W than among B or O pts with DLBCL (IRR W:B 1.52, 95% CI 1.45-1.59, W:O 1.26, 95% CI 1.21-1.31) and among those with immunoblastic DLBCL but not thymic DLBCL. 65% of B pts compared to 37% of W pts presented at age ≤60 years (p<0.001). Among pts with complete staging (n=5,285), 54% of B compared with 47% of W and 41% of O pts presented with stage III/IV disease (W vs. B p=0.05, W vs. O p=0.002). There were no differences in 2-yr RSR by gender. 2-yr RSR rates were 53% for W, 49% for O, and 46% for B pts (W vs. B p=0.02, W vs. O p=0.09), and improved from 1992 to 2001 for all racial groups. 5-yr RSR rates varied by race (46% for W, 47% for O, and 38% for B pts; (W vs. B p=0.02, W vs. O p=0.09) and gender (47% for females and 43% for males; p=0.03) and remained stable from 1992 to 1997.

These data indicate that B pts present with DLBCL at a younger age, more advanced stage, and have inferior 2-yr and 5-yr RSR. Given the known differences in outcomes for activated B-cell (ABC) and germinal center B-cell DLBCL subtypes, to address these differences in survival it will be necessary for future studies investigating racial disparities in treatment outcomes to ascertain whether there are racial differences in the incidence of ABC DLBCL.

Flowers:Amos Medical Faculty Development Program grant from the American Society of Hematology/Robert Wood Johnson Foundation: Research Funding.