Methylome analysis for prediction of long and short-term survival in glioblastoma patients from the Nordic trial

Patients with glioblastoma (GBM) have a short survival, but even among patients receiving the same therapies and with good prognostic factors, one can find those with exceptionally short and long survival. In the Nordic trial, patients with GBM, 60 years or older, were randomized between 2 radiotherapy arms or TMZ. We selected 59 patients, equally distributed between the 3 treatment arms and MGMT promoter methylation status, with good prognostic factors, but with short or long survival. We performed methylation profiling with the Illumina Infinium Methylation EPIC BeadChip arrays in conjunction with a methylation-based CNS tumor classifier, analysis of differentially methylated CpG sites (DMCs) and pathway enrichment analysis. Samples classified as non-GBM IDH wildtype were excluded and in the analysis of long vs. short survivors with documented progression or tumor-related death, we found DMCs in the TMZ, MGMT promoter methylated group (123,510), as well as in the 60Gy, MGMT promoter unmethylated group (4,086) and 34Gy, MGMT promoter methylated group (39,649). The joint analysis of the RT arms revealed 319 DMCs in the MGMT unmethylated group but no differences for MGMT promoter methylated samples, or in any of the analyses independent of MGMT status. Interestingly, in the long-term survivors with methylated MGMT promoter treated with TMZ we found hypermethylation of the Wnt signaling and the platelet activation, signaling and aggregation pathways. We identified DMCs for both TMZ and RT treated patients. Further systematic analysis of larger patient cohorts is necessary for confirmation of their predictive properties. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the Swedish Cancer Foundation, FORSS South-East Sweden Research Grant and a grant from ALF. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of Linkoeping University gave ethical approval for this work (permissions 99086, M11-06 T40-09 and 2011/32-32). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors and online at