P11.10.A An assessment of predictive factors for overall survival in glioblastoma - MGMT methylation is solely important for younger patients

Abstract

Abstract Background Diverse groups of factors - neuropathological characters, tumor position and epidemiological data - have been proposed for outcome evaluation of glioblastoma (GBM). We compared clinical signs, neuropathological features and the locus of the tumor with the follow-up data. Material and Methods All adult patients with firstly diagnosed and histologically proven GBM (according to WHO 2016), which were operated in our center between January 2010 and June 2021 were retrospectively assessed. Epidemiological, clinical and neuro-pathological characteristics were acquired from our institutional neuro-oncological database. Results A total of 399 patients could be evaluated. The mean follow-up was 13.9 months (CI95 12.2-15.6), within 266 (67%) patients were deceased. Estimated mean OS for entire cohort was 24.2 months (CI95 19.8-28.7). Age, MGMT promoter methylation, brainstem localization or if a patient received biopsy only showed significant impact on OS. Each year of life accounted for 3.4% additional hazard to decease (HR=1.034, CI95 1.020-1.048, p<0.001). If patients were younger than 65 years, mean OS was 34 months (CI95 26.5-41.8) compared to older than 65 years patients with a mean OS of 14.3 months (CI95 10.5-18.1, p<0.001). Generally, an unmethylated MGMT promoter status was linked to 75% higher hazards to decease (HR 1.75, CI95 1.27-2.40, p=0.027). If MGMT promoter status was methylated, mean OS was 25.7 months (CI95 19.9-31.5) or more compared to unmethylated with 14.5 months (CI95 12.0-16.9, p=0.01). Presence of MGMT promoter methylation showed influence on OS only in the younger cohort (<65y, mean OS 38.7 months [CI95 28.9-48.6]; HR 2.60 [CI95 1.55-4.37], p<0.001) as opposed to unmethylated MGMT (mean OS 17.7 months [CI95 14.1-21.2], p<0.001). In the older cohort (>65y) presence of methylated MGMT promoter showed no significant difference (p=0.364). For patients who received only biopsy, 2.4 times more hazards for worse OS were revealed (HR 3.36, CI95% 2.30-4.90, p<0.001). In these cases, mean OS was 7.1 months (CI95 5.3-8.8). Other factors, including gender or preoperative seizures, as well as EGFR, p53, IDH1, ATRX and TERT status did not show impact on OS in our series. Conclusion In our cohort, MGMT promoter methylation showed an impact on OS only in younger patients <65 years of age. Biopsy of GBM should only be considered very selected patients when resection is not possible.