Differences in childhood leukemia incidence and survival between Southern Thailand and the United States: a population-based analysis.

BACKGROUND: Childhood leukemia incidence and survival varies globally, and this variation may be attributed to environmental risk factors, genetics, and/or disparities in diagnosis and treatment.

PROCEDURE: We analyzed childhood leukemia incidence and survival trends in children aged 0-19 years from 1990 to 2011 in Songkhla, Thailand (n = 316) and compared these results to US data from the Surveillance, Epidemiology, and End Results (SEER) registry (n = 6,738). We computed relative survival using Ederer II and estimated survival functions using the Kaplan-Meier method. Changes in incidence and 5-year survival by year of diagnosis were evaluated using joinpoint regression and are reported as annual percent changes (APC).

RESULTS: The age-standardized incidence of leukemia was 3.2 and 4.1 cases per 100,000 in Songkhla and SEER-9, respectively. In Songkhla, incidence from 1990 to 2011 significantly increased for leukemia (APC = 1.7%, P = 0.031) and acute lymphoblastic leukemia (ALL) (APC = 1.8%, P = 0.033). Acute myeloid leukemia (AML) incidence significantly increased (APC = 4.2%, P = 0.044) and was significantly different from the US (P = 0.026), where incidence was stable during the same period (APC = 0.3%, P = 0.541). The overall 5-year relative survival for leukemia was lower than that reported in the US (43 vs. 79%). Five-year survival significantly improved by at least 2% per year from 1990 to 2011 in Songkhla for leukemia, ALL, and AML (P < 0.050).

CONCLUSIONS: While leukemia and ALL incidence increased in Songkhla, differences in leukemia trends, particularly AML incidence, may suggest etiologic or diagnostic differences between Songkhla and the US. This work highlights the importance of evaluating childhood cancer trends in low- and middle-income countries.