P11.80.a double blind randomised trial with add-on of valganciclovir or placebo to standard therapy of newly diagnosed glioblastoma

Abstract BACKGROUND The origin of glioblastoma is not known. Our earlier and other groups research have shown the presence of cytomegalovirus in glioblastoma, but not in adjacent tumor-free tissue. Furthermore there is a significant correlation between the amount of virus proteins in the tumor and prognosis, patients with low tumoral load have longer survival compared to patient with hogh tumoral viral load. In a retrospective study with 100 newly diagnosed patients with glioblastoma we showed tha the addition of valganciclovir yielded a median survival of 25 months as compared to 13 months for contemporary controls from the same institution. In the case of maximal surgical resection, the median survival reached 29 months. We therefore aimed to run a randomised doule blind study in newly diagnosed glioblastoma. MATERIAL AND METHODS The study started in September 2019, and has the goal to recruit 220 patients, 110 in the valganciclovir group and 110 in the placebo. A macroscopic surgery (at least 90% resection of contrast enhancing tumor on post op MRI), followed by radiation and chemotherapy with temozolomide. Patients receive the study drug, 900mg twice daily during the first 6 weeks, followed by maintenance 450mg twice daily for 2 years. There is no cross-over. The use of Optune is allowed. There is a stratification for MGMT methylation status. Only IDH1 wt tumors can be included, and the randomization has to take place within 10 weeks from surgery. The primary outcome is overall survival, secondary endpoints are the proportion surviving at 2 years and quality of life. 20 patients who fullfilled inclusions criteria have not been randomised. RESULTS since September 2019, 120 patients have been included at Karolinska Hospital in Stockholm. The oncology clinics in Oslo and Stavanger started including patients in September 2022, and have so far included 20 patients. At Karolinska there are 47 MGMT methylated and 73 unmethylated. Nineteen deceased patients and 45 deceased respectively. The median survival is 22 and 14 months respectively. Forteen patients with MGMT methyl completed the study (24 months and 6 months follow-up) versus 8 in the unmethylated. The survival of 20 patients not randomised was 18 months. Five patients showed reversibel hematological side effects grade 3-4, always with the initial high dose and concomittant to radiochemotherapy. No patient stopped the study due to side effects. CONCLUSION the is an ongoing trial, that has recruited about 35 patients per year at the main center, even during the 2 years of pandemics. about half of newly diagnosed patients are eligible for this study, and more than 80% of eligible patients are randomized which is remarkable for this category of patients. There may be a trend as a group for positive survival results, but we need to wait the final results, which may be available in 2-3 years. The study wil recruit until December 2024.