NCOG-03. DESCRIPTIVE ANALYSIS AND OUTCOME COMPARISON BETWEEN PATIENTS WITH GLIOBLASTOMA MULTIFORME WHO RECEIVE 15 VERSUS 30 FRACTIONS OF RADIOTHERAPY: A RETROSPECTIVE CHART REVIEW

Abstract The morbidity and efficacy of abbreviated radiotherapy (RT) courses for Glioblastoma (GB) in patients over 60 years have been studied, however, outcomes in younger patients are not yet well-described. This study aims to characterize the outcomes of patients receiving either a standard versus abbreviated RT course. A retrospective chart review at Kingston Health Sciences Centre from June 2014 to March 2021 included patients with GB receiving either 40Gy in 15 fractions (Fr) or 60Gy in 30Fr. Data on age, ECOG score, and concurrent chemotherapy (Temozolomide, TMZ) were collected. Outcomes compared were treatment completion, hospital admission during treatment, progression-free survival (PFS), and overall survival (OS). Records of 156 patients (median age 61 years, range 25-87 years) were reviewed. Of these, 89 received 30Fr and 67 received 15Fr (p=0.51). MGMT methylation was recorded in 54 (35%) patients; of these, 27 received 15Fr and 27 received 30Fr. Median follow-up was 12 months. While PFS did not significantly differ between 15Fr vs. 30Fr (6 vs. 11 months, respectively; p=0.08), OS was significantly different (8 vs. 16 months, respectively; p<0.001). Patients receiving 15Fr vs 30F tended to have higher ECOG scores (p<0.001) and were older (median: 71 [range 45-87] vs. 57 [range 25-69] years; p<0.001). Individuals receiving TMZ were more likely to receive 30Fr (67.5% vs. 32.5% for 15Fr; p<0.001). Completion rates were higher for 30Fr (94.3%) than 15Fr (83.6%; p=0.03). Hospital admission rates did not differ (p=0.51). In summary, patients receiving 15Fr (40Gy) typically have poorer functional status, are less likely to receive chemotherapy, and less likely to complete treatment compared to those receiving 30Fr. Hospital admission rates during treatment are low (13%) and similar for both groups. OS, but not PFS, is better for patients receiving 30Fr compared to 15Fr.