Racial Variations in Disease Characteristics, Presentations, Treatments, and Outcomes in Chronic Lymphocytic Leukemia (CLL)

Introduction: Our current understanding of CLL biology and optimal therapies is based on clinical trials that have largely enrolled White patient populations. Whether these findings are applicable to Hispanic or non-White patients is unknown but critical to evaluate given the growing numbers of minority patients in the U.S. While retrospective studies have suggested inferior outcomes in non-White patients, prospective data on these disparities are lacking.

Patients and Methods: We utilized the Mayo Clinic CLL database to better understand variations in disease characteristics, molecular differences, and treatment selections between non-Hispanic White patients and those not in this category (referred to hereafter as “other race”). After excluding 49 patients with missing diagnosis date and another 490 patients with missing race and/or ethnicity, the remaining 4104 cases within the registry were included in the analysis. Comparisons by race were made using Chi-square or Wilcoxon rank sum tests for qualitative or quantitative variables, respectively. Overall survival (OS) was calculated from diagnosis until death or last known alive date; time to first treatment (TTFT) was calculated from diagnosis until treatment date or date last known to be untreated. OS and TTFT were displayed via Kaplan-Meier plots, and differences in OS and TTFT by race were calculated using log-rank statistics. Individuals who were enrolled in early intervention trials (n=61) were excluded from analyses involving treatment.

Results: In total, 4104 CLL patients were identified: 4011 (97.7%) non-Hispanic Whites and 93 (2.3%) other races. Median age at CLL diagnosis was younger for other race patients (59 vs. 63 years; p=0.002), while gender and stage distributions were comparable between both groups. Serum β-2-microglobulin and absolute lymphocyte counts at diagnosis were similar but more other race patients had elevated LDH (29.5% vs. 16.1%; p=0.02). Cytogenetic data by FISH were available for 1884 non-Hispanic Whites and 46 other race patients; poor-risk cytogenetics (17p and/or 11q deletions) were present in 23.9% of other race and 13.5% of non-Hispanic White patients, respectively (p=0.04). No statistically significant differences were observed for CD38, ZAP-70, or IGHV by race

TTFT was similar for both non-Hispanic Whites and other race patients (4.6 vs. 5.5 years, respectively; p=0.12). First-line treatment selection was similar for both groups (Table). . With a median follow-up of 12.1 years, median overall survival was 9.3 years for other race and 12.2 years in non-Hispanic White patients (P=0.15; Figure).

Conclusions: This prospective data supports the notion that CLL might be biologically different between non-Hispanic White and other race patients with less favorable FISH present in the latter group. Despite the observation that TTFT and type of first therapy are similar between both groups, the trend towards shorter OS in other race patients argues that other factors might contribute to outcome differences, such as disease biology, access to care, co-morbidities, and socioeconomic considerations. Further studies with larger cohorts are warranted.

Figure:

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Overall survival in CLL cases stratified by race

Figure:

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Overall survival in CLL cases stratified by race

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