IMG-08. VOLUMETRIC MEASUREMENT OF TUMOR SIZE OUTPERFORMS STANDARD TWO-DIMENSIONAL METHOD IN EARLY PREDICTION OF TUMOR PROGRESSION IN PEDIATRIC GLIOMA

BACKGROUND: Pediatric brain tumors (PBTs) are the leading cause of cancer-related death in children. Currently, based on the RAPNO guidelines, two-dimensional (2D) measurements are used to detect progression. However, due to the complex radiographic appearance of many PBTs, 2D measurements may not accurately reflect tumor growth. Here, we compared 3D, 2D, and qualitative radiologists’ interpretations in a group of PBTs to determine tumor progression. METHODS: Six PBT patients (5 low-grade glioma, 1 ependymoma, age range at the time of baseline scan: 23-191 months) with an average of 5 imaging time points who had at least one episode of progression with subsequent surgery were included. Segmentation was performed on either T1 post-contrast or FLAIR, whichever that best identified the tumor. For 2D measurements, the two largest perpendicular diameters in a section that included the largest tumor component were measured. For the volumetric assessment, the tumors were manually segmented, and the volume was computed using the ITK-SNAP software. In multifocal tumors, only the tumor component that showed progression and underwent resection was included. A 25% and 41% increase in tumor size was considered as progression on 2D and 3D measurements, respectively. The time to progression (TTP) based on 2D vs 3D assessment as well as the official pediatric neuroradiologist interpretation based on the electronic health record report was compared. RESULTS: In three of six patients, volumetric segmentation detected tumor progression at an earlier time point compared to 2D measurements and radiologists’ interpretation (median TTP: 134 compared to 503 for 2D and radiologist interpretation). For these three patients, the TTP based on 3D vs 2D assessment was: 252 vs 1299 days, 134 vs 503 days, and 80 vs 255 days. CONCLUSION: Volumetric measurements can determine tumor progression earlier than the current standard method of 2D measurements and qualitative interpretation of radiologists in PBTs.