BACKGROUND: Pediatric acute myeloid leukemia (AML) is a rare hematopoietic cancer with few known risk factors. Some studies have found associations between exposure to certain environmental toxicants and AML among children, though results have been inconsistent across studies. On March 27, 2015, the Texas Department of State Health Services (DSHS) was notified of an abnormally high number of cases of pediatric acute myeloid leukemia (AML) diagnosed in a south Texas clinic. Between March and July 2015, a total of 8 cases were diagnosed at the clinic. The reporting physician and clinical staff were concerned about possible environmental exposures or other shared risk factors, given the dates of onset, close geographic proximity of case residences, and widespread agricultural activity in the area. DSHS investigated to assess possible environmental exposures or other risk factors shared by reported cases.
METHODS: DSHS epidemiologists reviewed Texas Cancer Registry incidence data for the census tracts and counties of case residences. Standardized Incidence Ratios (SIRs) and 95% Confidence Intervals were calculated to determine if the incidence of AML was greater than expected in cases’ combined counties of residence, compared to incidence rates in Texas in 2013. Only cases reported during this investigation were included in analyses and may underestimate the true number of pediatric AML cases diagnosed in these counties in 2015. In June 2015, DSHS conducted site visits and in-person interviews with seven case families. Interviews included questions regarding parental, pre- and perinatal, and childhood exposures. In addition, DSHS epidemiologists reviewed environmental data regarding: Superfund or other hazardous waste sites; public drinking water quality; air quality; Toxic Release Inventory facilities; and pesticide exposure complaints investigated by the Texas Department of Agriculture.
RESULTS: Between March and July 2015, a total of 8 AML cases of varied molecular subtypes were diagnosed at the clinic. Cases ranged from 0-18 years of age at diagnosis. Seventy-five percent were female and 100% were Hispanic. Four lived within a five-mile radius of each other. The 8 reported cases represented a statistically significant excess of pediatric AML cases in the combined counties of residence (SIR: 2.62; 95% CI: 1.13, 5.17). Questionnaire results did not reveal exposures potentially shared by cases but rare among the general population of south Texas. Specific exposures of concern were not identified from available environmental data.
CONCLUSIONS: Given the lack of information about possible exposures, no environmental or biological samples were collected. DSHS continues to monitor cancer rates in the area.