233. Ventricular Access Devices to Facilitate Liquid Biopsy in Pediatric Diffuse Midline Glioma: Literature Review and Evaluation of Institutional Practices

Authors: Daphne Li, MD; wendy stellpflug, BSN; kathy romanski; Maureen Killgallon; stacy speck; Amanda Saratsis, MD (Chicago, IL)

Introduction: Diffuse midline glioma (DMG) is the number one cause of pediatric cancer death. Up to 80% harbor an H3K27M mutation, detectable in circulating tumor DNA in the cerebrospinal fluid (CSF).  Given the relative morbidity of CSF sampling compared to tumor tissue biopsy, ventricular access devices (VAD) may play a valuable role in longitudinal monitoring of DMG patients via liquid biopsy. To determine the safety and feasibility of serial VAD access for this purpose, we characterize VAD placement and access practices in the pediatric population.

Methods: Retrospective review of patients <21 years treated at our institution for DMG (1984-2019) or neonatal post-hemorrhagic hydrocephalus (PHH, 2009-2019). A MEDLINE search for reports of VAD placement and access for pediatric DMG, neonatal PHH, or intraventricular chemotherapy (IVC).

Results: Of 108 DMG patients identified, 63.9% (n=69) had VADs: 20.3% transient (3 ETV, 9 EVD, 2 unspecified), 54.8% permanent (13 reservoirs, 42 shunts). Complications occurred in six patients (5.6%, six shunt malfunctions, one infection). Seventeen articles describing 289 DMG patients cited hydrocephalus in 22-100% requiring VAD placement in 22-63%, with ten non-infectious complications and one infection. Seven articles describe reservoir placement for IVC in 624 patients, 42 (6.5%) with infections and 51 (7.9%) with non-infectious complications, some in the same patient. Five articles describe CSF reservoir placement for PHH in 205 infants, with 2-100 punctures/device, infection in 0-32.4% and 14 non-infectious complications. Evaluation of our institutional PHH treatment complication rates is currently underway.

Conclusions: A significant proportion of pediatric DMG patients undergo VAD placement with low complication rates, while additional children undergoing serial VAD access demonstrate low morbidity.  As CSF analysis is increasingly considered for DMG management, VAD placement could be considered to facilitate longitudinal monitoring via liquid biopsy.