Pediatric brain tumor survivors treated with proton radiation therapy (PRT) prior to 4 years of age are at high risk for poor cognitive and developmental outcomes. This cross-sectional study examined developmental outcomes and educational service utilization at follow-up in a cohort of pediatric survivors treated with PRT before the age of 4 years.

A total of 46 patients (58.7% female, 93.5% White) were assessed using age-appropriate measures for executive, behavioral, and adaptive functioning. Mean age at PRT was 2.4 years (SD=0.9, range 1.0-3.9 years); mean age at follow-up was 7.0 years (SD=4.8, range 2.0-18.6 years). Mean follow-up interval was 4.57 years (SD=4.52, range 0.9-16.2 years). Diagnoses included ependymoma (n=26, 54.2%), medulloblastoma (n=7, 14.6%), craniopharyngioma (n=4, 8.3%), and a few other tumor types. Infratentorial tumors were most common (69.6%). Treatment included prior surgical resection (93.5%) and chemotherapy (60.9%). Posterior fossa syndrome was present in 10.9% (n=5). PRT field consisted of focal (n=41, 89.1%) or craniospinal irradiation (CSI) (n=5, 10.9%). The impact of demographic, diagnostic, and treatment-related factors was examined, including age at PRT, gender, time interval since PRT, radiation field, and tumor location, on intelligence quotient (IQ), adaptive skills, and executive functioning. Rates of impairment (T-scores >65) were calculated. The utilization of educational services was determined.

Mean IQ (SS = 97.6, SD=16.3), as well as mean global executive functioning (Mean T=53.4, SD=11.1) and adaptive skills (Mean SS = 92.5, SD=21.4), as assessed by parent rating scales (BRIEF; SIB), were in the average range. Despite mean scores being within the average range, a large proportion of patients demonstrated difficulties with social withdrawal (28.3%) and activities of daily living (28.3%) (BASC), and global executive dysfunction (17.4%) (BRIEF). Younger age at PRT was associated with lower global adaptive skills at follow-up (r=.39, p=.005), better activities of daily living (r=.53, p<.001), lower social skills (r=.43, p=.002), and more hyperactivity (r=-.37, p=.008), but not aggression, anxiety, depression, somatization, atypical behaviors, withdrawal, or attention problems. Longer follow-up interval was correlated with better activities of daily living (r=.46, p<.001), but more anxiety (r=.39, p=.006). Gender, SES, radiation field, history of hydrocephalus, and location of tumor were not significantly related to primary outcome variables. Posterior fossa syndrome was associated with lower adaptive skills (t=2.90, p=.003) and IQ (t=2.02, p=.026). Of those enrolled in school, 59% received special education services and/or accommodations (IEP n=18, Early Intervention n=6; 504 Plan n=3).

Overall, PRT before age 4 years was associated with difficulties with withdrawal, adaptive skills, and executive functioning. Younger age at PRT was associated with lower adaptive functioning, lower social skills, and higher hyperactivity, but not with IQ, attention, mood, or anxiety. While a longer time interval since treatment was associated with improvement in activities of daily living, anxiety was increased, suggesting some late emotional effects. Furthermore, posterior fossa syndrome after surgery was related to lower adaptive skills and IQ. Attention problems were not indicated. Approximately half received school services/accommodations. Young children treated with PRT require proactive support and services to foster their developmental outcomes.