Predictive significance of mean apparent diffusion coefficient value for responsiveness of temozolomide-refractory malignant glioma to bevacizumab: preliminary report

Background

Recurrent glioblastoma after initial radiotherapy plus concomitant and adjuvant temozolomide is problematic. Here, patients with temozolomide-refractory high-grade gliomas were treated with bevacizumab (BV) and evaluated using apparent diffusion coefficient (ADC) for response.

Methods

Nine post-temozolomide recurrent or progressive high-grade glioma patients (seven with glioblastoma and two with anaplastic astrocytoma) were treated with BV monotherapy. Average age was 57 years (range, 22–78), median Karnofsky Performance Scale (KPS) was 70 (30–80) and median BV line number was 2 (2–5). Two had additional stereotactic radiotherapy within 6 months prior to BV. Magnetic resonance (MR) imaging after BV therapy was performed within 2 weeks with calculation of mean ADC (mADC) values of enhancing tumor contours.

Results

Post-BV treatment MR imaging showed decreased tumor volumes in eight of nine cases (88.9 %). Partial response was obtained in four cases (44.4 %), four cases had stable disease, and one had progressive disease. Of 15 evaluable enhancing lesions, 11 shrank and four did not. Pretreatment mADC values were above 1100 (10^?6 mm²/s) in all responding tumors, while all non-responding lesions scored below 1100 (p = 0.001). mADC decreased after the first BV treatment in all lesions except one. KPS improved in four cases (44.4 %). Median progression-free survival and overall survival for those having all lesions with high mADC (>1100) were significantly longer than those with a low mADC (<1100) lesion (p = 0.018 and 0.046, respectively).

Conclusions

Bevacizumab monotherapy is effective in patients with temozolomide-refractory recurrent gliomas and tumor mean ADC value can be a useful marker for prediction of BV response and survival.