Abstract 1784: Disparities in pediatric leukemia incidence and survival: a population-based cancer registry analysis comparing Thailand and the United States
Authors: Demanelis Kathryn , Sriplung Hutcha , Meza Rafael , Wiangnon Surapon , Rozek Laura S. , Scheurer Michael E. , Lupo Philip J. 
Published: July 2016

Abstract
Background: Pediatric leukemia incidence and survival varies worldwide. This variability may be due to differences in genetics, environmental factors, and access to treatment and diagnosis. However, more work is needed to elucidate patterns of pediatric leukemia in developing countries including Thailand. Therefore, we analyzed pediatric leukemia incidence and survival trends in children age 0-19 years from 1990-2011 in Thailand and compared these results to United States (US) data. We evaluated the following pediatric leukemia subtypes: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML).
Methods: We extracted pediatric leukemia cases from five provincial population-based cancer registries in Thailand (n = 1,245). Cases from the US were obtained from the Surveillance, Epidemiology, and End Results program (n = 6,738). We computed age-standardized incidence rates (ASIR) using the WHO 2000 standard population and relative survival using the Ederer II method and estimated survival functions using the Kaplan-Meier method. We evaluated temporal changes in incidence and survival by year of diagnosis and estimated annual percent changes using joinpoint regression.
Results: While the ASIR of ALL was lower in Thailand compared to the US (21.1 vs. 31.2 cases per million), the ASIR of AML was similar between Thailand and the US (7.7 vs. 7.7 cases per million). The proportion of ALL and AML diagnosed in Thailand was 60% (n = 746) and 23% (n = 284), respectively, vs. 75% (n = 5,080) and 19% (n = 1,267) in the US (p&lt;0.001). The mean age at diagnosis was significantly older in Thailand compared to the US for both ALL (7.2 vs. 6.5 years, p &lt;0.001) and AML (9.9 vs. 9.0 years, p = 0.047). ALL incidence increased by 1.5% per year in Thailand (p = 0.015) while it increased by 0.9% per year in the US (p = 0.003). AML incidence increased by 2.3% per year in Thailand (p = 0.047) while it remained constant in the US. Five-year survival significantly improved in Thailand between the first (1990-2000) and second half (2001-2011) of our study period for both AML (19% to 29%, p = 0.009) and ALL (45% to 55%, p = 0.001). ALL and AML five-year survival was 86% and 54% in the US. ALL survival increased by 1.5% per year in Thailand (p = 0.022) while it increased by 0.7% per year in the US (p &lt;0.001). AML survival increased by 1.8% per year in the US (p &lt;0.001). Due to variability in survival by year, no trend was identified in Thailand.
Conclusion: The incidence of both ALL and AML increased more rapidly in Thailand than in the US from 1990-2011. While five-year survival for pediatric leukemia improved in Thailand, it was much lower than in the US. These disparities in incidence and survival warrant: 1) investigating novel population risk factors for pediatric leukemia, especially AML, in Thailand and 2) identifying diagnostic and treatment disparities to address the survival gap between Thailand and the US.
Citation Format: Kathryn Demanelis, Hutcha Sriplung, Rafael Meza, Surapon Wiangnon, Laura S. Rozek, Michael E. Scheurer, Philip J. Lupo. Disparities in pediatric leukemia incidence and survival: a population-based cancer registry analysis comparing Thailand and the United States. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1784.