The goal of this observational study is to find out what factors affect the health and risks in adults with glioblastoma (GBM), a grade 4 brain cancer. The main questions it aims to answer are: * How do genetic and immune system factors impact survival and quality of life in GBM patients? * What occupational and medical history factors are linked to the risk of getting GBM? Participants will: * Fill out an online survey about their medical history and lifestyle. Participants will have the chance to give a blood sample (from the outer arm) for genetic and immune system testing. Blood samples will be given using a home collection kit provided by the study team.