P14.65 Survival in a consecutive series of 467 glioblastoma patients: impact of prognostic factors and recurrent treatment at two independent institutions

BACKGROUND Glioblastoma (GBM) is an aggressive primary brain tumor with median overall survival (OS) of less than one year in unselected adult patients. There is no standard therapy at recurrence. We aimed to evaluate OS in a consecutive series of GBM patients from Norway’s two largest regional health authorities, compare the effect of physicians’ choice of antineoplastic treatment upon recurrence and identify prognostic and predictive factors. MATERIAL AND METHODS Clinicopathological data from n=467 patients with histologically confirmed GBM diagnosed and treated at Haukeland and Oslo university hospitals from January 2015 to December 2017 was retrospectively collected. Data included tumor location, methylation status of the methylguanine-DNA methyltransferase (MGMT) promoter and mutation of the isocitrate dehydrogenase (IDH) genes, patient age and sex, extent of tumor resection at primary diagnosis, and treatment at first, second and third tumor recurrences. Cox-proportional hazards regression with pairwise analyses adjusted for multiple testing with Scheffé’s post-hoc test were used to adjust effect of multiple risk factors on mortality. RESULTS Median OS was 12.1 months and 21.4 % and 6.8 % of patients were alive at 2 and 5 years, respectively. Treatment at recurrence varied between institutions but did not impact OS (p=0.201). Median time to progression was 8.2 months. Age, MGMT promoter methylation, tumor location and extent of tumor resection were all independent prognostic factors for OS. Patients receiving radiotherapy to 60 Gray with concomitant and adjuvant temozolomide at primary diagnosis had best outcome with median OS of 16.1 months and 9.3% were alive at 5 years. At first recurrence patients eligible for gammaknife/stereotactic radiosurgery (GK/SRS) or surgery, alone or combined with chemotherapy, had superior survival compared to chemotherapy alone (p CONCLUSION Recurrence treatment differed between the two institutions but there was no difference in OS. Our findings underline the lack of standard therapy upon GBM recurrence and the urgent need for novel therapeutic strategies.