SURP-01. Clinical Impact of Intratumoral Cyst Decompression in Diffuse Intrinsic Pontine Glioma Patients: A Retrospective Analysis

Abstract Diffuse Intrinsic Pontine Gliomas (DIPG) have a poor prognosis with median overall survival between 9 to 12 months. Biopsies have been increasingly used for molecular characterization and to guide novel biomarker-driven therapies, however, their impact on cyst formation remains unclear. Similarly, there are no guidelines on management of brainstem cysts. In this retrospective analysis, we aimed to determine whether cyst development in patients with DIPG is associated with prior biopsy and whether cyst drainage improved neurologic symptoms and allowed for prolonged systemic therapy. We retrospectively analyzed the charts of 83 DIPG patients from between 2020-2024. Patient characteristics including age, H3K27 mutation status, sex, prior CAR T-cell infusions, prior radiation treatments, prior biopsy, cyst formation, and decompression were reported. Associations between patient variables and cyst development were assessed using logistic regression. Forty-five (54.2%) patients underwent biopsy. Seventeen patients (20.5%) developed cysts, 14 of which had undergone biopsy and 11 of which were receiving CAR T-cell therapy. Cyst formation was not significantly correlated with age (OR 1.07, p = 0.158), male sex (OR 1.66, p = 0.358), prior CAR T-cell therapy (OR 1.26, p = 0.758), or prior biopsy (OR 3.11, p = 0.116). Six patients with worsening symptoms from cyst expansion underwent cyst decompression. Five of these patients were receiving CAR T-cell therapy and had a intra-cyst catheter placed that could be subsequently tapped. Patients exhibited improved neurological symptoms with repeated drainage over weeks to months. All five decompressed patients who were also receiving CAR T-cell therapy were able to receive additional infusions following decompression. There is no clear association between biopsy and intratumoral cyst development in DIPG. Preliminary findings suggest that drainage allows for symptomatic relief and continuation of systemic therapies such as CAR T-cell infusions.