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 in glioblastoma with promising results.

Senator John McCain’s diagnosis of a particularly aggressive brain cancer, glioblastoma (GBM), became public knowledge. But what exactly is this type of cancer, and what does it mean for the senator and other patients? A report by Roche estimates that there are around 240,000 cases of brain and nervous system tumors diagnosed worldwide per year, with GBM being the most common and the most lethal. Even in recent American history, it has claimed the lives of both Senator Edward Kennedy and Beau Biden, son of former Vice President Joe Biden.

GBM is a very aggressive form, or a Grade IV, type of brain tumor called an astrocytoma. It’s a type of glioma, a brain tumor that begin in the glial cells that surround and support neurons. Those can include anything from general neurologic symptoms, like headaches or seizures, to symptoms that stem from specific areas of the brain, like speech difficulty, weakness on one side of the body, or double vision.

O’Brien estimates that there are around 2 or 3 cases of GBM for every 100,000 people in America. It is the most common form of primary brain tumor (a cancer that begins in brain tissue) and in most cases it does not spread to any part of the body. There aren’t really any known risk factors, except for that it’s mostly found in people in their fifties, sixties, and older, and it’s slightly more common in men. Very rarely, it can be seen hereditarily in people with certain genetic syndromes such as neurofibromatosis type 1, Turcot syndrome, and Li Fraumeni syndrome.

GBM is typically diagnosed through brain imagery and then surgery. O’Brien says that if a patient experiences symptoms of a brain tumor, it’s necessary to see a physician to get the ball rolling on diagnosis through imaging. “If the brain imaging, such as an MRI, does show or is suspicious for glioblastoma, the next step is for surgery,” she says. “After the surgeon removes the tumor tissue, a pathologist evaluates it and confirms the diagnosis for glioblastoma.”

Treatment includes removing as much of the tumor as possible, and then beginning radiation and chemotherapy. As of right now, O’Brien says, there is no definitive cure for this type of tumor. So doctors focus on maintaining the patient’s quality of life by keeping the mass from growing. O’Brien says that the term remission isn’t used for GBM, and that the average survival rate post-diagnosis is less than two years. However, a 2009 study showed that around 11 percent of the subjects treated with radiotherapy along with temozolomide survived for five years.

With more research, perhaps. O’Brien says that there are a variety of other potential solutions being explored, like vaccines, viruses, and therapies called checkpoint inhibitors.