Glioblastoma
Glioblastoma, also known as glioblastoma multiforme (GBM), is the most aggressive cancer that begins within the brain. Initially, signs and symptoms of glioblastoma are non-specific. They may include headaches, personality changes, nausea, and symptoms similar to those of a stroke. Worsening of symptoms often is rapid. This may progress to unconsciousness.
The cause of most cases is unclear. Uncommon risk factors include genetic disorders such as neurofibromatosis and Li–Fraumeni syndrome, and previous radiation therapy. Glioblastomas represent 15% of brain tumors. They can either start from normal brain cells or develop from an existing low-grade astrocytoma. The diagnosis typically is made by a combination of CT scan, MRI scan, and tissue biopsy.
There is no clear way to prevent the disease. Typically, treatment involves surgery, after which chemotherapy and radiation therapy are used. The medication temozolomide is used frequently as part of chemotherapy. High dose steroids may be used to help reduce swelling and decrease symptoms. It is unclear whether trying to remove all or simply most of the cancer is better.
Despite maximum treatment, the cancer usually recurs. The most common length of survival following diagnosis is 12 to 15 months, with fewer than 3% to 5% of people surviving longer than five years. Without treatment, survival is typically three months. It is the most common cancer that begins within the brain and the second most common brain tumor, after meningioma. About 3 per 100,000 people develop the disease a year. It most often begins around 64 years of age and occurs more commonly in males than females. Immunotherapy is being studied.
Common symptoms include seizure, headaches, nausea and vomiting, memory loss, changes to personality, mood or concentration, and localized neurological problems.
Glioma
Epigenetic repression of DNA repair genes is often found in progression to sporadic glioblastoma. For instance, methylation of the DNA repair gene "MGMT" promoter was observed in 51% to 66% of glioblastoma specimens. In addition, in some glioblastomas, the MGMT protein is deficient due to another type of epigenetic alteration. MGMT protein expression may also be reduced due to increased levels of a microRNA that inhibits the ability of the "MGMT" messenger RNA to produce the MGMT protein. Zhang et al. found, in the glioblastomas without methylated "MGMT" promoters, that the level of microRNA miR-181d is inversely correlated with protein expression of MGMT and that the direct target of miR-181d is the "MGMT" mRNA 3’UTR (the three prime untranslated region of "MGMT" messenger RNA).