(510) Epilepsy with encephalopathy as a late effect of chemoradiation in survivors of various early childhood cancers with CNS involvement; a pediatric case series

Rationale: As survivorship of pediatric cancers and brain tumors improves, further delineation of long-term morbidities is critical. Seizures are known to be a common complication of both primary central nervous system tumors and oncologic processes with central nervous system involvement (Wells et al. 2018, Maytal et al. 1995). Seizures occur most frequently during induction or consolidation therapy but there is a growing body of evidence that they can also develop as a late finding, particularly in the setting of high-dose radiation therapy (Wells et al 2018) which is hypothesized to be secondary to a treatment related neurotoxicity (Gonzalez-Otarula et al 2016). However, further characterization of this epilepsy syndrome is not well studied. This study presents three cases of late-onset epilepsy in patients with history of early childhood CNS oncologic disease treated with both chemotherapy and cranio-spinal radiation who presented to epilepsy care with both encephalopathy and frequent seizures.

Methods: Patients of the senior author, referred to the Epilepsy Center at Lurie Children’s Hospital of Chicago between 2018 and 2020 were reviewed. A retrospective chart review was undertaken for these three patients and we analyzed information including but not limited to: demographics, clinical presentation, imaging findings, EEG results, clinical course, and outcome at follow-up visits.

Results: All three patients presented for spells concerning for seizures and underwent EEG monitoring between two and seven years after receiving chemoradiation therapy for different types of cancers with CNS disease. Each EEG study displayed both diffuse moderate cerebral dysfunction and multiple areas of epileptogenicity. None had evidence of oncologic recurrence. Two patients displayed subsequent improvement in both seizure frequency and encephalopathy after initiation of anti-seizure medications; the third patient died prior to scheduled follow-up.

Conclusions: Epilepsy with encephalopathy can develop in survivors of early childhood CNS oncologic disease many years after initial chemoradiation therapy, independent of disease recurrence. It is important to recognize the potential relation between chemoradiation and the development of epilepsy in this fashion for caregiver counseling, to expedite evaluation in these rare cases and to improve morbidity and mortality in this vulnerable population.

Funding: Please list any funding that was received in support of this abstract.: None