That’s for sure. I am unfortunately very familiar with Glioblastoma. Lost my beloved niece, my dear cousins husband, and a good friend for 25 years. They all died within 14 to 20 months of diagnosis. I am familiar with two other people, not first hand, but one died within six months another did live about two years. Not knowing what his treatment is but as I recall every intrusion into the brain for treatment, (resection of the fast growing tumor, chemo wafer implantation, biopsies, etc) All leave a deficit to the brain.
1 to 2 year survival is possible with the best treatment he is getting for brain cancer.