Racial differences in the presentation and outcomes of chronic lymphocytic leukemia and variants in the United States

Abstract

Background: Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia in the United States, and prolymphocytic leukemia (PLL) is a related, rare chronic lymphoproliferative disorder.

Methods: Using the United States Surveillance, Epidemiology and End Results (SEER) data from 13 registries, we examined differences in incidence and survival for CLL, small lymphocytic lymphoma (SLL) and PLL by race. International Classification of Diseases for Oncology 3(rd) edition histology codes 9670, 9823, and 9632-34 were used to identify cases.

Results: From 1992 to 2007, 30,622 cases of CLL/SLL and 268 cases of PLL were recorded. Males had higher incidence than females (male-to-female incidence rate ratio CLL/SLL 1.89, 95% confidence interval (CI) 1.85-1.94 and PLL 2.47, 95%CI 1.90-3.20). Black patients were diagnosed at younger age compared to white patients (mean age at diagnosis for white versus black patients for CLL/SLL, 70 versus 67 years, P < .001; for PLL, 71 versus 61 years, P < .001). Greater proportion of black patients with SLL presented with B symptoms, extranodal primary site, and advanced disease compared to white patients (P = .003, P = .012, and P = .009 respectively). White patients with CLL/SLL had better survival rates than black patients (5-year relative survival rate 77.1% versus 63.9%, P < .01). In univariate Cox regression models, black race, male gender, age at diagnosis > 65 years, advanced stage, and B-symptoms were predictors of worse survival (P < .01) among CLL/SLL patients.

Conclusions: Black patients with CLL/SLL and PLL present at younger age and black patients with CLL/SLL have worse survival than white patients. Epidemiological studies examining the biological variants of these diseases in concert with race are needed to elucidate the etiology of these disparities.