Geographic Variation in Pediatric Cancer Incidence — United States, 2003–2014

Approximately 15,000 persons aged <20 years receive a cancer diagnosis each year in the United States (1). National surveillance data could provide understanding of geographic variation in occurrence of new cases to guide public health planning and investigation (2,3). Past research on pediatric cancer incidence described differences by U.S. Census region but did not provide state-level estimates (4). To adequately describe geographic variation in cancer incidence among persons aged <20 years in the United States, CDC analyzed data from United States Cancer Statistics (USCS) during 2003-2014 and identified 171,432 cases of pediatric cancer during this period (incidence = 173.7 cases per 1 million persons). The cancer types with the highest incidence rates were leukemias (45.7), brain tumors (30.9), and lymphomas (26.2). By U.S. Census region, pediatric cancer incidence was highest in the Northeast (188.0) and lowest in the South (168.0), whereas by state (including the District of Columbia [DC]), rates were highest in New Hampshire, DC, and New Jersey. Among non-Hispanic whites (whites) and non-Hispanic blacks (blacks), pediatric cancer incidence was highest in the Northeast, and the highest rates among Hispanics were in the South. The highest rates of leukemia were in the West, and the highest rates of lymphoma and brain tumors were in the Northeast. State-based differences in pediatric cancer incidence could guide interventions related to accessing care (e.g., in states with large distances to pediatric oncology centers), clinical trial enrollment, and state or regional studies designed to further explore variations in cancer incidence.

from Nevada, which did not meet criteria in 2011. This report includes all cases of malignant † cancer diagnosed among persons aged <20 years; it includes first primary cases only and excludes recurrent cases. Diagnosis histology and primary site were grouped according to the International Classification of Childhood Cancer (ICCC). § Pediatric cancer rates were expressed per 1 million persons and were age-adjusted to the 2000 U.S. standard population. ¶ Rates were estimated by sex, age group, race/ethnicity, state, U.S. Census region,** county-level economic status, countylevel rural/urban classification, and ICCC group.
Rates were highest in the Northeast U.S. Census region, followed by the Midwest, the West, and the South. Rates were highest in the Northeast across all age groups and among whites and blacks. Among Hispanics, rates were highest in the South. Pediatric cancer incidence rates were highest in the 25% of counties with the highest economic status and were higher in metropolitan areas with populations ≥1 million than in nonmetropolitan areas.
By state, pediatric cancer incidence rates ranged from 145. 2 Massachusetts 3,584 181.5 (175.6-187.5) Delaware 504 180.9 (165.5-197.5)    Pediatric cancer incidence rates varied by state within each cancer type (Figure). Incidence rates were highest in the West for leukemias, myeloproliferative diseases, and myelodysplastic diseases (ICCC group I) and in the Northeast for lymphomas and reticuloendothelial neoplasms (group II) and central nervous system cancers (group III). Rates were also highest in the Northeast for neuroblastoma, retinoblastoma, bone tumors, soft tissue sarcomas, and thyroid cancer (Supplementary Table 2, https://stacks.cdc.gov/view/cdc/53586). Renal cancer rates were highest in the Northeast and South; hepatic tumor rates were highest in the Northeast and West. Germ cell tumor rates were highest in the West (Supplementary Table 2, https:// stacks.cdc.gov/view/cdc/53586).

Discussion
This study used recent data with greater population coverage than past studies (4,5) to document geographic variation in pediatric cancer incidence rates by sex, age, type, and race/ ethnicity. Consistent with past reports (1,4,5), pediatric cancer rates were highest in males, persons aged 0-4 years and 15-19 years, whites, and the Northeast U.S. Census region. Rates were highest in metropolitan areas with populations ≥1 million; state-based rates were highest in New Hampshire, DC, and New Jersey.
A strength of this report is the use of extensive populationbased surveillance data (>99% coverage § § ), which permits a The ICCC group total map includes 258 cases not classified by ICCC. ¶ Incidence data are compiled from cancer registries that meet the data quality criteria for all years 2003-2014 (covering >99% of the U.S. population). Nevada is excluded. Registry-specific data quality information is available at https://www.cdc.gov/cancer/npcr/uscs/pdf/uscs-2014-technical-notes.pdf. detailed description of state-based cancer incidence variation. Geographic variation in rates might account for differences in results from previous studies that were based on different populations such as state data (2,3), SEER registries (which cover 9%-28% of the U.S. population), ¶ ¶ or other large data sets (6). A 2016 study specific to Delaware assessed pediatric cancer incidence by demographic group and ZIP Code; the study commented on local environmental exposures and possible incidence disparities based upon sex, age, race/ethnicity, geographic location, and economic status (2). USCS data provide states with a standardized way to gauge whether local pediatric cancer incidence rates differ relative to other states and might prompt states to conduct investigations similar to the one performed in Delaware.

Summary
What is already known about this topic?
Past research on nationwide pediatric cancer incidence described differences by U.S. Census region but did not provide state-level estimates.
What is added by this report?
During 2003-2014, the pediatric cancer rate was highest in the Northeast, lowest in the South, and highest in metropolitan areas with populations ≥1 million and counties in the top 25% economic status. Incidence rates by state ranged from 145 to 206 per million and were highest in New Hampshire, the District of Columbia, and New Jersey. The highest rate of leukemia was in the West; the highest rates of lymphoma and brain cancer were in the Northeast.
What are the implications for public health practice?
Knowledge of these geographic differences in childhood cancer incidence can be used to enhance provider awareness, treatment capacity, survivorship care, and cancer surveillance.
certain cancer types might vary by race/ethnicity. For example, Hispanic children have the highest rate of the most common type of leukemia, pediatric acute lymphoblastic leukemia, and states with a higher proportion of Hispanics might have higher rates of acute lymphoblastic leukemia (8). Fourth, incidence of some types of cancer (e.g., thyroid carcinoma) might be related to enhanced detection and access to care, which can vary by geographic location (5,9).
In addition, geographic variation might be affected by age, economic status, or rural/urban classification (4,8,10). Similar to the findings from this report, recent data detailing adult cancers also indicate that the highest cancer incidence rates are in the Northeast (10). Rates of cancer types mostly affecting adults also varied by rural/urban status; some of these differences in adults might be related to factors such as obesity or smoking (10), which might or might not also explain rural/ urban variation in pediatric cancer.
The findings in this report are subject to at least three limitations. First, Nevada was excluded because data for 2011 did not meet quality criteria, which limits the representativeness of the findings. Second, differences in diagnosis and cancer reporting among states might contribute to variation in cancer incidence rates (8). For example, states that were early adopters of electronic pathology reporting might report increased rates because of increased case ascertainment compared with other states. Finally, misrepresentation of race and ethnicity might exist; rate numerators might underestimate American Indians, Alaska Natives, and Hispanics, which could artificially lower rates among these groups; and U.S. Census populations used in rate denominators might undercount children and Hispanics, which could artificially increase rates in these populations (8). † † † Knowledge of pediatric cancer incidence variation by state and cancer type can prompt local and state cancer registries to evaluate reporting and diagnostic standards. Understanding geographic variation in incidence rates can help cancer control planners and clinicians address obstacles in access to care, which is especially relevant to states with large distances to pediatric oncology centers (3). Because 5-year pediatric cancer survival is >80%, and most cancer survivors require close monitoring by specialists throughout life (5), state-specific data by cancer type and patient age might help public health planners address ongoing chronic care needs. In addition, state-specific data by cancer type and patient age might help clinical trial organizers predict patient accrual. Finally, health care practitioners and researchers can use these data to guide investigations related to causes of pediatric cancer incidence variation (2,3). Continued surveillance will be needed to further validate findings and track geographic incidence patterns over time. † † † https://www.cdc.gov/cancer/npcr/uscs/technical_notes/interpreting/race.htm.