Radiographic patterns of relapse in glioblastoma

Glioblastoma (GBM) pathologically is defined as an infiltrative glioma and salvage therapy with bevacizumab is believed to increase the incidence of diffuse and distant invasion as assessed radiographically. Eighty adult patients with glioblastoma were treated with surgery followed by radiotherapy (RT) and concurrent and adjuvant temozolomide (TMZ). At first recurrence, 80 patients were treated with single agent bevacizumab. At time of progression, 57 patients were treated with bevacizumab and a cytotoxic chemotherapy, cytotoxic chemotherapy alone or on an investigational trial. Magnetic resonance imaging (MRI) were analyzed at four time points in each patient; at presentation, at first, second and third recurrence. Four patterns of radiographic disease were assessed, local (unifocal disease), distant (second lesion noncontiguous with primary lesion), multifocal (>2 lesions including leptomeningeal dissemination) and diffuse. At presentation 87.5% of glioblastoma were local, 6.25% distant, 3.75% multifocal and 2.5% diffuse. At first recurrence following progression on RT/TMZ and before initiation of bevacizumab, 80% were local, 7.5% distant, 6.25% multifocal (including 1 with CSF dissemination) and 6.25% diffuse. At second recurrence following progression on bevacizumab, 71.25% were local, 8.75% distant, 8.75% multifocal (2/7 with CSF dissemination) and 11.25% were diffuse. At third recurrence (57 patients evaluable), 71.25% were local, 7.0% distant, 7.0% multifocal and 14.0% were diffuse. Survival following progression on bevacizumab did not differ by pattern of radiographic recurrence. A majority of adult patients with GBM at diagnosis manifest MRI-defined local disease and maintain this pattern notwithstanding multiple recurrences and treatment with bevacizumab.