Diffusion histogram analysis predicts progression-free survival in contrast enhancing recurrent IDH mutant gliomas treated with bevacizumab.

BACKGROUND: Pretreatment apparent diffusion coefficient (ADC) histogram analysis-specifically the lower Gaussian peak mean (ADC-L)-is a predictive biomarker of progression-free survival (PFS) and overall survival (OS) in recurrent IDH-wildtype glioblastoma receiving anti-VEGF treatment including bevacizumab. IDH-mutant gliomas differ biologically from glioblastoma, as they exhibit lower tumor cellularity, longer survival, and distinct sensitivity to a variety of therapies. Whether ADC-L retains predictive utility in IDH-mutant recurrent glioma has not been established. METHODS: In this retrospective, single-center study, sixty patients with IDH-mutant recurrent glioma (41 astrocytoma, 19 oligodendroglioma) with measurable contrast enhancement and available pretreatment diffusion-weighted MRI who received bevacizumab were analyzed. Univariate and multivariate Cox regression and Kaplan-Meier analyses were performed for PFS and OS. RESULTS: The optimal ADC-L threshold was 1.19 μm2/ms. High ADC-L (≥1.19 μm2/ms) was associated with significantly longer PFS (median 5.46 vs. 2.76 months; p = 0.006) but not OS. In multivariate analysis, low ADC-L (HR = 2.054; p = 0.0228) and astrocytoma histology (HR = 2.295; p = 0.0158) were independent predictors of shorter PFS when accounting for number of prior recurrences. ADC-L was also significant predictor of PFS in both astrocytoma and oligodendroglioma patients, independently, after accounting for number of recurrences. CONCLUSIONS: Pretreatment ADC-L predicts PFS in IDH-mutant recurrent glioma receiving bevacizumab. Supporting prospective evaluation of ADC-L as a biomarker for bevacizumab patient selection in this population.