Single institution analysis of glioblastoma multiforme (GBM) outcomes based on year of diagnosis: A 17 year review.

e14023 Background: GBM is the most common brain tumour in adults. The latest WHO classification excludes IDH mutated tumours, acknowledging their favourable prognosis. MGMT methylation is a prognostic biomarker and predicts level of benefit from Temozolomide. The standard of care management includes maximal surgical resection followed by radiotherapy with concurrent and adjuvant Temozolomide. This has remained largely unchanged for nearly 20 years. We analysed 17 years of newly diagnosed GBM cases attending Medical Oncology at our institution to assess outcome advancements. Methods: Demographic information, clinicopathological characteristics, surgery, radiotherapy and systemic anti-cancer treatment data were collected from the charts of patients diagnosed with GBM and seen by the Medical Oncology department at Cork University Hospital between 2005-2021. The study population was divided into 2 time periods: 2005-2016 and 2017-2021. Overall survival was recorded. Baseline characteristics was compared across time periods using the Chi-Square test. Univariate and multivariate analysis was performed to assess impact of different variables on overall survival. Results: The analysis comprised 306 patients, with 142 and 164 diagnosed between 2005-2016 and 2017-2021 respectively. Median age was 62 years (range 17-86) and patients were predominantly male (65%). Patients in the earlier time period were more likely to have ECOG performance status 0-1 (80% vs 65% p = 0.011) and were more likely to commence treatment on Stupp protocol (99% vs 80% p = 65, MGMT status, ECOG performance status, steroid use, surgery, re-resection, and completion of adjuvant chemoradiation protocols. The mOS was 12.3 months in the earlier time period and 10.4 months in the later time period (HR = 1.35 p = 0.012). Time period of diagnosis remained an independent prognostic factor for poor outcome on multivariate analysis. Notably, mOS during the COVID-19 pandemic (2020-2021) was 10.6 months, showing no difference from other time periods. Conclusions: Despite advances in our knowledge regarding the molecular biology of GBM, prognosis remains poor. Our institution’s 17 year survival data indicates no improvement over time emphasising the urgent need for new treatment strategies. Notably, the more recent time period had an increased number of frailer patients who were too unwell to commence any adjuvant treatment, possibly indicating a lower referral threshold which may have negatively impacted mOS in that cohort. Additionally, the absence of IDH status assessment in the earlier era means some IDH mutant patients were likely included, thereby inflating the mOS for that cohort.