Response Assessment of Meningioma: 1D, 2D and Volumetric Criteria for Treatment Response and Tumor Progression.

Background: Meningiomas are the most common primary brain tumors in adults. Due to their variable growth rates and irregular tumor shapes, response assessment in clinical trials remains challenging and no standard criteria has been defined. We evaluated 1D, 2D, and volume imaging criteria to assess whether a volumetric approach might be a superior surrogate for overall survival (OS).

Methods: In this retrospective multicenter study, we evaluated the clinical and imaging data of 93 patients with recurrent meningiomas treated with pharmacotherapy. 1D, 2D, and volumetric measurements of enhancing tumor on pre- and post-treatment MRI were compared at 6 and 12 months after treatment initiation. Cox proportional hazards models were used to examine the relationship between each imaging criterion and OS.

Results: The median age of the patient cohort is 51 years old (range 12-88), with 14 WHO grade 1, 53 WHO grade 2, and 26 WHO grade 3 meningiomas. Volumetric increase of 40% and unidimensional increase by 10 mm showed the highest hazard ratios versus OS at both 6 months (HR= 2.58, 95%CI: [1.31-5.07], p=0.006) and 12 months (HR= 3.24, 95%CI: [1.49-7.0], p=0.002) after treatment initiation. Volume threshold above 40% did not show improved survival association. The inter-observer agreement of 1D, 2D and volume criteria is only moderate (kappa=0.49, 0.46, 0.52 respectively). None of the criteria based on tumor size reduction were associated with OS (p>0.09).

Conclusion: Compared to 1D (RECIST 1.1) and 2D (RANO) approaches, volumetric criteria for tumor progression has a stronger association with overall survival, although the differences were only modest. The inter-observer variability is moderate for all three methods. Further validation of these findings in an independent patient cohort is needed.