UCSF

Abstract PURPOSE/OBJECTIVE(S): Identify prognostic factors for progression-free survival (PFS) and overall survival (OS) after reirradiation (re-RT) for recurrent high grade glioma (HGG). MATERIALS/

METHODS

Patients with HGG received re-RT from 2010 to present. PFS and OS prognostic variables were examined using Cox models. Receiver operative curve (ROC) analysis identified predictive thresholds for continuous variables.

RESULTS

58 patients received surgery and adjuvant radiation for HGG (51 grade IV, 7 grade III). The median time to first progression after initial radiation was 11 months. 36% received single fraction stereotactic re-RT (SRS) (median 18 Gy) and 64% received fractionated re-RT (median 35 Gy in 10 fractions). The median planning target volume (PTV) was 16.8 mL. The median biologically effective dose (BED10) of re-RT was 47 Gy (range 15–72). 50% received chemotherapy and 36% received bevacizumab concurrent to re-RT. Toxicity ≥ grade 3 was 7%. The median PFS after re-RT was 4.7 months and the median OS was 11 months. Lower PFS was significantly associated with shorter time to first progression, lower KPS, and lower re-RT dose. Lower OS was associated with shorter time to first progression, lower KPS, and larger PTV. Other factors were not significantly associated with PFS or OS. ROC analysis of time to first progression and re-RT dose showed best predictive thresholds at time > 12 months and BED10 > 42 Gy. CONCLUSIONS: Reirradiation was tolerated with infrequent high grade toxicity. PFS and OS after re-RT were both predicted by time to progression after initial radiation. Published prognostic scores have used total time from first to second radiation courses; however in our series the period from initial progression to re-RT did not add prognostic information. There was evidence for a dose threshold irrespective of radiotherapy technique. Use of chemotherapy and bevacizumab with re-RT were not associated with improved outcomes.