Abstract
BACKGROUND: Corticosteroids, which are commonly used in the clinical management of glioblastoma, are known to impact the radiographic interpretation of glioblastoma. In particular, corticosteroids can induce an apparent reduction in contrast-enhancing tumor volume and intensity (i.e., a “pseudoresponse”), as well as a reduction of the apparent coefficient diffusion (ADC) from diffusion imaging. This study aimed to estimate the influence of corticosteroids on these measurements in treatment naïve glioblastoma before surgery. METHODS: 57 pairs of MRI scans from 54 patients with pre-surgical treatment-naïve glioblastoma were retrospectively grouped as increased (n=29), stable (n=25), or decreased (n=3) corticosteroid dose between scans (median interval: 15 days). All cases with steroid increase (n=29) and the majority of cases stable (n=21) with stable steroids were off steroids at the first timepoint. Tumor size and ADC changes between timepoints were compared between lesions with increased and stable corticosteroids. Volumetric changes ascribable to increased corticosteroid dose was modeled, adjusting for the time between scans. RESULTS: Increased corticosteroid dose showed an observed volumetric shrinkage of the contrast-enhancing tumor (median shrinkage: 23.7%) and reduction in estimated growth rates, significantly different (p<0.0001) from the control group receiving a stable dose (median growth: 36.0%; with 2.08% growth rate). When adjusting for the interval growth between scans, while comparing the two groups, the estimated corticosteroid-induced volumetric shrinkage was 44.0% (p<0.0001, 95%C.I. 25.7–62.2%). Increased corticosteroid dose also caused an ADC drop in the contrast-enhancing tumor (median ADC reduction: 180, IQR=39–281×10(-6) mm(2)/s, p=0.0005). CONCLUSION: Corticosteroid administration induce a significant “pseudoresponse” in glioblastoma. Providing benchmark quantitation of this phenomenon is crucial for the future development of adjusted response criteria accounting for corticosteroid use. Additionally, a quantitative estimate of corticosteroid-induced ADC reduction can lead to corticosteroid-adjusted ADC measurements, potentially improving diffusion imaging applications for differential diagnosis, molecular profiling, and prognosis stratification.