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MO_15_2846 - Safety and Efficacy of Proton Beam Therapy for High-Grade Glioma: Initial Report From the Proton Collaborative Group(PCG)

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

Safety and Efficacy of Proton Beam Therapy for High-Grade Glioma: Initial Report From the Proton Collaborative Group(PCG)
S. A. Vora1, V. Gondi2, Y. D. Tseng3, C. E. Vargas4, G. L. Larson5, H. K. Tsai6, L. M. Halasz7, and L. R. Rosen8; 1Mayo Clinic Arizona, Phoenix, AZ, 2Northwestern Medicine Chicago Proton Center, Warrenville, IL, 3Seattle Cancer Care Alliance Proton Therapy Center, Seattle, WA, 4Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 5ProCure Proton Therapy Center, Oklahoma City, OK, 6ProCure Proton Therapy Center, Somerset, NJ, 7University of Washington, Department of Radiation Oncology, Seattle, WA, 8Willis-Knighton Proton Therapy Center, Shreveport, LA

Purpose/Objective(s): Little published data exists on proton beam therapy for treatment of newly diagnosed high grade glioma. Using a prospective, multiinstitutional prospective registry, we report on outcomes and acute toxicity for a cohort of patients with high grade glioma treated with proton therapy.

Materials/Methods: We queried a multiinstitutional collaborative registry for patients with newly diagnosed grade 3 or 4 high grade glioma treated with proton therapy and who had at least one post-treatment follow-up. Pathology was reviewed locally and classified per 2007 WHO classification. Patients received proton therapy for the entire treatment course. Toxicity was graded according to CTCAE v4.0. Descriptive statistics were used to present patient, tumor and treatment characteristics. Kaplan-Meier method was used to calculate rates of overall survival (OS).

Results: Sixty-three patients underwent definitive proton beam therapy for grade 3 or 4 glioma at 6 institutions between 2009 and 2017. Median follow-up was 15.0 months (range 2.4-73.2 months). Median age was 56.0 years with 36 males and 28 females. 73 % were grade 4 and 27% were grade 3. IDH1 status was available for 38% of the cohort (71% IDH1 wild-type, 29% mutant). MGMT status was available for 35% (27% methylated, 73% unmethylated). 54% underwent gross total resection, 29% underwent subtotal resection and 17% underwent biopsy only. 89% received concurrent temozolomide with radiation. Median dose delivered was 59.4 GyE (range 40-66 GyE), which was given over 15-33 fractions. Median OS was 18.3 mos with 2 year OS 39.0%. Median OS was significantly improved for younger patients (<70 vs ≥70 years: 22.5 vs 14.5 mo.; log rank p=0.0003) and those with grade 3 tumors (grade 3 vs grade 4: not yet reached vs. 17.0 mos; p=0.0026). MGMT methylation status was not found to be predictive (p=0.65). Proton therapy was well tolerated, with acute CTCAEv4.0 grade 1/2 symptoms such as alopecia, headache, ataxia, confusion, insomnia and dermatitis seen in all patients. 3 patients (4.6%) developing grade ≥3 acute toxicity (1 grade 3 headache, 1 grade 3 fatigue, 1 grade 4 thrombocytopenia) .

Conclusion: This study represents the largest group of high grade glioma patients treated with proton therapy. Proton therapy was well tolerated and outcomes are comparable to photon based historical controls.

Author Disclosure: S.A. Vora: None. V. Gondi: None. Y.D. Tseng: Employee; Allen Brain Science Institute. C.E. Vargas: Independent Contractor; Florida Radiation Oncology Group. Stock; View Ray. Chairman; Proton Collaborative Group. G.L. Larson: Independent Contractor; Procure Proton Therapy Center - Oklahoma City. Stock; Procure Proton Therapy Center - Oklahoma City. L.M. Halasz: Research Grant; Fred Hutch/Univ of Washington Cancer Consortium. L.R. Rosen: Partner; Radiation Oncology Services. Honoraria; Iba, lane r rosen. Speaker's Bureau; lane r rosen. Travel Expenses; Iba, lane r rosen. Stock; IBA. Board Member; Caddo bossier cancer foundation league.

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