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MO_1_2488 - Reirradiation of Recurrent High Grade Gliomas: Outcomes and Prognostic Factors

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Reirradiation of Recurrent High Grade Gliomas: Outcomes and Prognostic Factors
C. H. Chapman1, J. Hara2, J. Clarke3, N. A. Butowski3, S. M. Chang3, S. E. Fogh4, P. K. Sneed4, J. L. Nakamura5, D. Raleigh5, and S. E. Braunstein4; 1University of California San Francisco, Department of Radiation Oncology, San Francisco, CA, 2University of Hawaii, John A. Burns School of Medicine, Honolulu, HI, 3University of California San Francisco, Department of Neurological Surgery, San Francisco, CA, 4University of California, San Francisco, San Francisco, CA, 5University of California, San Francisco, Department of Radiation Oncology, San Francisco, CA

Purpose/Objective(s): Identify prognostic factors for progression-free survival (PFS) and overall survival (OS) after reirradiation (re-RT) for recurrent high grade glioma.

Materials/Methods: An institutional database was queried for patients with high grade glioma (HGG) who received re-RT for progressive disease from 2010 to present. PFS and OS after re-RT were estimated using the Kaplan-Meier method, and prognostic variables were examined using univariate and multivariate Cox models. Receiver operative curve (ROC) analysis was used to determine best predictive thresholds for continuous variables.

Results: 58 eligible patients had received surgery and adjuvant radiation ± temozolomide for initial diagnosis of HGG (51 grade IV, 7 grade III). The median time to first progression after initial radiation was 11 months. Prior salvage therapy before re-RT included chemotherapy (60%) and surgery (45%). The median number of separate progression events before re-RT was 1 (range 0 – 5). The median time from first progression to re-RT was 2.7 months, and from initial radiation to re-RT was 18 months. 36% received single fraction stereotactic re-RT (SRS) (median 18 Gy, range 14 – 19 Gy) and 64% received fractionated re-RT (median 35 Gy in 10 fractions, range 10 – 60 Gy in 2 – 30 fractions). The median biologically effective dose (BED10) of re-RT was 47 Gy (range 15 – 72). The median planning target volume (PTV) was 16.8 mL (range 0.4 – 783.6). 50% received concurrent chemotherapy and 36% received bevacizumab concurrent and/or adjuvant to re-RT. Acute (≤ 3 months) toxicity ≥ grade 3 was 7%. The median PFS after re-RT was 4.7 months (1 year PFS 18%), and the median OS was 11 months (2 year OS 21%). By univariate analysis, lower PFS was significantly (p<0.05) associated with shorter time to first progression after initial radiation, lower KPS, and lower re-RT dose (BED10). Lower OS was associated with shorter time to first progression after initial radiation, lower KPS, and larger PTV. Time from initial RT to re-RT, time from first progression to re-RT, use of SRS, and chemotherapy or bevacizumab at re-RT 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. All significant univariate factors retained significance on multivariate analysis except re-RT dose (p = 0.07).

Conclusion: Reirradiation was well tolerated with infrequent high grade acute toxicity. PFS and OS after re-RT for high grade glioma 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 of BED10 > 42 Gy (> 16 Gy in 1 fraction, 27.5 Gy in 5 fractions, or 32 Gy in 10 fractions) irrespective of radiotherapy technique. Use of chemotherapy and bevacizumab with re-RT were not associated with improved PFS or OS.

Author Disclosure: C.H. Chapman: Employee; University of California San Francisco. Travel Expenses; University of California San Francisco. J. Hara: None. J. Clarke: None. N.A. Butowski: None. S.M. Chang: None. P.K. Sneed: Honoraria; CareCore National, LLC. Travel Expenses; CareCore National, LLC. Board Member; North American Gamma Knife Consortium. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.

Christopher Chapman, MD, MS

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