METHODS
In this retrospective, population-based cohort study, we included
children between the ages of 0-19 years newly diagnosed with primary CNS
tumors between 2000 - 2015 in the Surveillance, Epidemiology, and End
Results (SEER) Program sponsored by the National Cancer Institute (NCI).
These population-based cancer registries include all incident cancer
from 18 geographical locations in the US representing more than 28% of
the US population.23 SEER collects demographic,
clinical, treatment and survival information on all incident cancers
(excluding non-melanoma skin cancer). Tumor histology is classified
using International Classification of Diseases for Oncology (ICD-O-3)
codes.24 We additionally received special permission
to access the Specialized Census Tract-level SES and Rurality Database
developed by SEER. In these data, socioeconomic status for patients
represented by Yost quintile reflects the SES group for the patients’
census tract of residence at the time of disease (see below for measure
definition). 25,26 The SES Yost quintile
classification of census tracts is based on a time dependent composite
score of the social and economic stratification of the area in which a
patient resides at the time of diagnosis.26
Cancers diagnosed only by direct visualization or clinical impression
without any imaging or laboratory confirmation were excluded from the
study (n=73). Cases diagnosed by autopsy or death certificate only were
also excluded (n=41), as were cases without information on their SES
(n=151). Patients who had the optic nerve as the primary site of tumor
were also excluded (n=723) from the data set due to its association with
neurofibromatosis and complex natural history and
therapy.27 Our final sample included 8,713 children
aged 0-19 at diagnosis.