Purpose: We studied corticosteroid-induced magnetic resonance (MR) scan changes in patients with recurrent malignant glioma to determine if corticosteroid therapy started concurrently with investigational treatment might yield false-positive responses.
Patients and methods: Ten symptomatic patients not on corticosteroids when malignant glioma recurred had a baseline MR scan performed before corticosteroid treatment, followed by serial scans at weekly intervals for 1 month while on dexamethasone (16 mg/d). The maximum cross-sectional areas and volumes of the gadolinium-enhancing regions (tumor) and T2-weighted abnormalities (tumor plus edema) were compared quantitatively and qualitatively for each series of scans.
Results: Nine of 10 patients (90%) had a measurable reduction in the size of the gadolinium-enhancing region or T2-weighted abnormality with corticosteroid treatment. The maximum cross-sectional area and volume of the gadolinium-enhancing region decreased by at least 25% in three of 10 patients (30%). The maximum cross-sectional area and volume of the T2-weighted abnormality decreased by at least 25% in five of 10 patients (50%). Maximum measurable radiologic improvement was evident within 2 weeks in most patients. MR scans were judged improved by the reporting neuroradiologist in seven of 10 (70%). These subjective visual improvements were also evident within 2 weeks, but generally described as slight or modest.
Conclusion: Corticosteroid-induced MR scan reductions in tumor size may confound the assessment of response of recurrent malignant gliomas to investigational agents. For patients who start corticosteroids for symptom control, investigational treatment should be delayed until a new baseline MR image is established 2 weeks later. Response is then judged by comparing subsequent MR scans with the new corticosteroid-influenced baseline image.