Assessment of non-measurable disease in high-grade glioma: rano-based 2d vs. 3d volumetrics

Abstract Non-measurable disease (NMD) in High grade glioma (HGG), defined as "longest perpendicular dimension of less than 10 mm”, is a limitation of RANO criteria that limits trial enrollment and biases trial populations to exclude patients with smaller tumors that eventually become measurable. Volumetric (3D) measurements may improve sensitivity and precision for measuring HGG of all sizes, however there is limited data comparing volumetric to 2D RANO measurements. AIMS: To investigate the correlation between RANO-based bidimensional 2D and 3D volumetric measurements in the postoperative setting of patients with HGG, including patients with NMD. METHODS: Contrast-enhanced (CE) postoperative and radiotherapy planning MRIs were utilized for 2D RANO measurements by neuroradiologists and volumetric (3D) measurements extracted from segmentations of CE disease. Pearson’s correlation between the 2D and 3D measurements were evaluated at each time point. The percentage of NMD based on RANO criteria and the range of tumor volumes for the NMD cases were reported. RESULTS: For 59 patients, there was lower concordance in the 2D and 3D measures at the postoperative MRI time point (Pearson =0.46) compared to the treatment planning MRI time point (Pearson=0.81). Interestingly, the postoperative time point had a higher percentage of NMD of 38% with the mean tumor volume of 13 cm3 (range: 0-21 cm3) compared to the treatment planning MRI with percentage NMD of 8% and mean tumor volume of 9 cm3 (range: 6-13cm3). CONCLUSION: In this study, higher rate of agreement was observed between RANO-based 2D and 3D volumetric tumor measurements at the time point of MR simulation when there was lower rate of NMD, suggesting NMD may contribute to the discrepancy between 2D and 3D measurements. Volumetric measurement tools may be a superior approach to improve the assessment especially of NMD in the postoperative period, improving trial enrollment for these patients.