I'm a physician.
I know of one case in which the husband of one woman and the son of her sister both died of glioblastoma multiforme. It seems obvious to me that whatever the causative agent is, it was passed on from these two sisters, from one to the husband, from the other to her son.
That seems like one hell of an inference. Could be a coincidence or there could be an environmental cause that didn't pass through the sisters.
My sister died of this - she made it 8 years but in the end complications of a stroke killed her. I am under frequent surveillance by the University of Washington because of family ties.
I have also heard that the Polio virus somehow helped to fight GBM. Of course, all of these new tools only extend the life of the patient and do not cure GBM. However, extending someone’s life is very important as I wish we had that capability when my father was diagnosed with GBM back in 2011. After having some disorienting headaches, he went from driving himself to the doctor for an MRI to leaving us 7 weeks later. This cancer is pure evil and ranks up there with Pancreatic Cancer for mortality rates.