535P Hypofractionated Radiotherapy in Fit Elderly Patients with Glioblastoma: Relevant or Detrimental?

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. It remains a relatively rare disease with an incidence of 3/100.000 in France, and an age-related peak in incidence at 70 years of age, which corresponds to the age limit inclusion criteria of the Stupp Trial on 2005, cornerstone of the GBM strategy. Therefore, treatment of GBM in elderly patients is not standardized and depends on several clinical and biological factors. The aim of this study is to compare survival outcome of elderly patients with glioblastoma treated with standard radiotherapy (SRT) versus hypofractionated radiotherapy (HRT) versus no radiotherapy (RT), with or without Temozolomide. A single-center retrospective case series analysis was conducted, including newly diagnosed GB patients older than 70 from January 2010 to December 2021. The Log-Rank test was used to compare the PFS and OS of patients treated with SRT versus HRT versus no RT. Furthermore, a Cox regression analysis was performed to identify risk factors associated with OS. Statistical significance was considered when p<0.05. A total of 304 patients were included with a median age of 74.36 years [71.63, 78.62], among whom, 142 were women. Most patients had a performans status of 0 or 1. Median OS was 11.4 months [95% CI 10.4 – 12.3] while median PFS was 8.1 months [95% CI 7.4 – 9.1]. Overall, 231 patients (76%) were treated with RT, 94 (30.9%) with SRT, 129 (42.4%) with HRT and 73 (24%) did not receive RT. On univariate analysis, the SRT group showed a better OS compared to the HRT and no RT groups (23.1 months, 11.1 months and 4.7 months, respectively, p<0.01). Same trend was observed for median PFS (SRT 13.6 months, 8.08 months and 3.7 months respectively, p<0.05). While previous randomized trials showed a benefit or non-inferiority of HRT over SRT in elderly glioblastoma patients, this large retrospective “real-life” cohort shows on the contrary a benefit in terms of OS of the standard normo fractionated RT regimen. Standard treatment should not always be degraded in elderly patient, and a proportion of them may still benefit from standard RT if their clinical status allows it.