Immediate post-radiotherapy changes in malignant glioma can mimic tumor progression.

To determine the frequency of progressive MRI lesions shortly after radiotherapy for glioma with spontaneous improvement or stabilization, the authors studied a cohort of patients treated within two prospective phase III trials with radiotherapy only. In 9 out of 32 patients, the first post-radiotherapy MRI showed progressive enhancement. In 3 of these 9 the MRI improved or stabilized for 6 months without additional treatment. The authors conclude that patients with progressive lesions within 3 months after radiotherapy should not be eligible for phase II trials on recurrent glioma.