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Inequalities by Race/Ethnicity and Socioeconomic Position in the Incidence and Survival of Childhood Acute Lymphoblastic Leukemia in the United States Open Access


Other title
health disparities
socioeconomic position
childhood cancer
Acute lymphoblastic leukemia
Type of item
Degree grantor
University of Alberta
Author or creator
Wang, Linwei
Supervisor and department
Yasui, Yutaka (School of Public Health)
Examining committee member and department
Yasui, Yutaka (School of Public Health)
Yuan, Yan (School of Public Health)
Gomez, Scarlett L (Stanford School of Medicine)
School of Public Health
Date accepted
Graduation date
Master of Science
Degree level
Background: Childhood acute lymphoblastic leukemia (ALL) is the most common childhood cancer in the United States. The incidence and survival of childhood ALL have been reported to be closely associated with race/ethnicity and socioeconomic position (SEP). However, the relationship between SEP and risk of childhood ALL is not conclusive. Racial and ethnic inequalities are known in survival after childhood ALL, yet it is unclear how these inequalities have changed over time in different race/ethnicity groups, following continued survival improvement over the last several decades. Objectives: The primary objectives of this thesis research were to: 1) quantify the incidence of childhood ALL by SEP, age and sex within each race/ethnicity; 2) investigate the association between census tract-level SEP and risk of childhood ALL, and examine potential racial and ethnic differences in the association; 3) investigate the trends of racial and ethnic inequalities in survival after childhood ALL over time; 4) quantify the racial and ethnic inequalities in survival within specific age at diagnosis and sex subgroups. Methods: This research was conducted using population-based cancer registries data from the National Cancer Institute Surveillance, Epidemiology and End Results (SEER) program in the United States. Children diagnosed with a first primary malignant ALL at age 0-19 years were included. Race/ethnicity was classified as non-Hispanic-Whites (NH-Whites), non-Hispanic-Blacks (NH-Blacks), Hispanics, Asian/Pacific Islanders (APIs), and American Indian/Alaska Natives (AIANs). Census tract-level composite SEP index was also obtained from the SEER data. Crude incidence rates of ALL by SEP, sex and age within each race/ethnicity group were calculated. Cumulative ALL mortalities were compared across different race/ethnicity groups. Incidence rate ratios and their 95% confidence intervals (CIs) associated with SEP and race/ethnicity, adjusting for sex, age and year of diagnosis, were estimated using Poisson regression models with log population counts as the offset term. Multivariable Cox regression analyses were applied to estimate ALL mortality hazard ratios (HRs) associated with race/ethnicity, age at diagnosis and sex, adjusting for each other, within each diagnosis period (1975-83, 1984-91,1992-99, and 2000-10). Results: The risk of childhood ALL was positively associated with SEP among NH-Whites, NH-Blacks, APIs, and AIANs, but was negatively associated among Hispanics. After adjusting for sex, age and year of diagnosis, as compared against children with the lowest SEP, the adjusted incidence rate ratios of children with the highest SEP were: 1.29 (95% CI, 1.15-1.44) for NH-Whites, 1.67 (95% CI, 1.20-2.34) for NH-Blacks, 1.57 (95% CI, 1.17-2.09) for APIs, 2.46 (95% CI, 0.98-6.19) for AIANs and 0.70 (95% CI, 0.60-0.81) for Hispanics. Racial and ethnic inequalities in ALL mortality among patients diminished in NH-Blacks, but increased in other racial/ethnic groups, as compared to NH-Whites, in particular among Hispanics. Specifically, compared to NH-Whites, the HR in NH-Blacks dropped to 1.21 (95% CI, 0.74-1.96) in 2000-10 from the largest inequality seen in 1984-91 (HR=2.09, 95% CI, 1.57-2.79); the HR in Hispanics increased, however, from 1.28 (95% CI, 0.98-1.66) in 1975-83 to 1.95 (95% CI, 1.48-2.58) in 2000-10. APIs and AIANs had HRs of 1.39 (95% CI, 0.92-2.11) and 2.31 (95% CI, 1.13-4.74), respectively, in 2000-10 with non-statistically significant increases over time. Conclusions: Associations between SEP and risk of childhood ALL differed by race/ethnicity. Future study should confirm this finding and investigate potential underlying causes. Survival inequalities changed differently across subgroups of children with ALL. Underlying causes of the differential trends need to be examined, such that targeted interventions can be developed to reduce inequalities.
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
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