Abstract B043: Racial and sex variability in pediatric ALL survival is explained by immunogenic subtypes
Authors: Holmes Larry , Herring Kijai , Dabney Kirk , Masire Phatsimo 
Published: August 2020

Purpose: Acute lymphocytic leukemia (ALL) is the most commonly diagnosed childhood malignancy. ALL survival has dramatically increased with an estimated 80% relative survival. Despite these advances, black children continue to present with survival disadvantages. We aimed to assess survival of ALL by race and sex, and to determine whether or not the survival disadvantage of black children was due in part to the immunogenic subtypes.

Methods: A retrospective cohort design was used to assess the Surveillance and Epidemiology End Result Data (SEER), 1973-2015 of children (0-19 years) with ALL. The variables assessed were ALL immunogenic types and social determinants of health as exposure function of survival. To assess the temporal trends, we used a generalized linear model. To assess survival, Kaplan Meir, Nelsen Aalen, log-rank test were utilized to test the equality of survival by race and sex. The Cox proportional hazard model was used to assess predictors of survival, while the global test of Shoenfeld was used to examine the cox proportional model assumption.

Results: There were 18,720 cases of ALL; 11,669 were B-ALL, 1,614 were T-ALL and 5,437 were unspecified. There was an increased temporal trend in ALL incidence percent change (52.9%), which was higher among blacks (106%) relative to whites (62.7%) and among female (75%) relative to male (38.5%). The odds of dying for whites was 0.24, 95% Confidence Interval (CI)=0.23-0.25, while the odds of dying for blacks was 0.35, 95%CI=0.31-0.40. Compared to whites, blacks with ALL were 42.1% more likely to die, hazard ratio (HR) = 1.42, 95% CI= 1.27-1.59. Relative to females, males were 30% more likely to die, HR=1.30, 95% CI= 1.21-1.39. Survival varied by immunogenic subtype, with T-ALL and ALL unspecified showing survival disadvantage relative to B-ALL. Children with T-ALL were 54% (HR=1.54, 95% CI=1.37-1.74), while children with ALL unspecified were 81% (HR= 1.81, 95% CI=1.68-1.94) more likely to die. Racial and sex variabilities in ALL survival was impacted by immunogenic subtype, implying increased risk of dying for blacks as exposure function of T-ALL, while increased risk of dying for male as an exposure function of B-ALL. After controlling for tumor prognostic factors, and the social determinants of health, blacks compared to whites with T-ALL were 61% more likely to die, adjusted HR (aHR)= 1.61, 99% CI= 1.10-2.39, while for B-ALL, blacks were 31% more likely to die, aHR=1.31, 99% CI= 1.03-1.66. In contrast, after controlling for the tumor prognostic factors and the social determinants of health, males with B-ALL were 21% more likely to die (aHR=1.21, 99% CI= 1.05-1.38), while for T-ALL males were 10% more likely to die albeit statistically insignificant (aHR= 1.0, 99%CI= 0.79-1.52).

Conclusion: Survival disadvantage of blacks and males with ALL existed and persisted after controlling for confounding factors, but was explained in part by immunogenic subtype, namely T-ALL, which is a more aggressive form of ALL and was most diagnosed among black and male children.

Citation Format: Larry Holmes Jr., Kijai Herring, Kirk Dabney, Phatsimo Masire. Racial and sex variability in pediatric ALL survival is explained by immunogenic subtypes [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr B043.