Susceptibility and Tumor Size Changes During the Time Course of Standard Treatment in Recurrent Glioblastoma

Susceptibility-weighted magnetic resonance imaging (SWI) yields information regarding tumor biology (e.g., hemorrhage) of growing gliomas. SWI changes can also be observed as a consequence of treatment, for example radiation therapy. The aim of our study was to investigate how susceptibility changes occur during the time course after completion of standard treatment in newly diagnosed glioblastoma (GBM).

Eighteen GBM patients were retrospectively analyzed. After completion of therapy, imaging was performed every 3 months. MRI was analyzed at the following time points: after the third and sixth cycle of adjuvant temozolomide chemotherapy, thereafter in 3 month intervals and at recurrence. The number of SWI positive tumor pixels was quantified and compared with progression as defined by the RANO criteria on T2- and contrast-enhanced T1-weighted MRI sequences (T1-CE).

The MRI interval between completion of the sixth chemotherapy cycle and last MRI before progression was 390 ± 292 days. Between the last MRI before progression and at progression a significant increase in SWI positive tumor pixels was observed (P = .012), whereas tumor size remained unchanged (RANO T2: P = .385; RANO T1-CE: P = .165). The number of SWI positive pixels remained unchanged between last MRI before progression until progression (P = .149), whereas RANO T2 and T1-CE showed tumor progression (interval 128 ± 69 days).

SWI positive pixel count increases significantly prior to changes in tumor size (RANO). Our findings may be explained by microbleeds compatible with stimulation of angiogenesis and possibly serve as an early biomarker of tumor progression.