Patterns of failure after radiosurgery to two different target volumes of enhancing lesions with and without FLAIR abnormalities in recurrent glioblastoma multiforme.

Glioblastoma multiforme (GBM) invades beyond enhancing boundaries, and tumor cells are believed to exist in edematous peritumoral regions. We hypothesize that the concomitant treatment of both enhancing and FLAIR abnormalities on MRI by fractionated radiosurgery (FRS) would reduce local and regional recurrence. The purpose of this study was to demonstrate patterns of failure after FRS with simultaneous differential doses to two different target volumes of contrast enhancing lesions with/without FLAIR abnormality in recurrent GBM. Fifty-three patients with recurrent GBM were treated with FRS between 2008 and 2012. FRS was offered for the patients who had progressive tumors after the initial surgical resection followed by chemoradiation, and second-line chemotherapy. Radiosurgery Regimen A was 32 Gy (8 Gy × 4 treatments) to the contrast enhancing lesion only. Regimen B was 32 Gy (8 Gy × 4) to the contrast enhancing lesion and 24 Gy (6 Gy × 4) to the FLAIR abnormality delivered concomitantly. The study endpoint was radiographic failure on MRI at 2 months after FRS. Median survival after FRS was 7.5 months, and median progression-free survival after FRS was 4 months. Overall 82.4 % (42/51 lesions) recurred during follow-up. The local and regional failure rate was significantly lower in Regimen B (52 %) than in Regimen A (86.7 %) (p = 0.003). No sign of tumor progression in 10 % of Regimen A versus 28.6 % of Regimen B was shown during followup (p = 0.04). Instead, distant failure rate was higher in Regimen B. In conclusions, FRS was found to be a safe and effective salvage therapy for recurrent GBM. FRS to both contrast enhancing and FLAIR abnormalities appeared to improve local tumor control, and reduce regional tumor progression.