Multilevel Factors Associated with Pediatric Leukemia: The Role of Rural Areas Adjacent to Urban Areas

Leukemia is the most prevalent form of malignant cancer among children zero to 14 years of age. Established risk factors encompass a range of environmental exposures and patient attributes such as age, gender, and race/ethnicity; additionally, a correlation exists between lower socioeconomic status and an unfavorable prognosis. This research investigated whether attributes of residential counties in the United States consistently distinguished between pediatric leukemia patients and pediatric cancer patients without leukemia after accounting for various patient-level factors. The units of analysis consisted of pediatric (age < 20 years) cancer diagnoses reported to the Surveillance, Epidemiology, and End Results "SEER-21" cancer registry from 2010 through 2017 (N=44,808). The outcome was binary: cases were pediatric leukemia diagnoses (9.69%), and controls were the remaining non-leukemia pediatric cancer diagnoses. County-level predictors included urban-rural status, inflation-adjusted median household income, and proximity to tribal lands. Patient-level factors included age, sex, ethnicity/race, the reporting source, and the year of diagnosis. Using multilevel logistic regression, nonmetro counties adjacent to metro counties had 30 percent greater odds that a pediatric cancer was leukemia compared to counties of metro areas with over one million residents. The crude association between lower county median household income and pediatric leukemia was confounded by this nonmetro county adjacent to metro result. Males and all minorities also had higher odds that a given pediatric cancer would be diagnosed as leukemia. Exploration of these patient factors alongside documented environmental risk factors for pediatric leukemia should be conducted among residents of nonmetro counties neighboring metro counties. This urban-rural discrepancy in the odds of leukemia among pediatric cancer diagnoses should improve the identification of localized risks and prevention efforts in these communities.