5 Things To Know About Glioblastoma, John McCain's Brain Cancer

WASHINGTON, DC — Sen. John McCain has been diagnosed with glioblastoma multiforme, a form of brain cancer that doctors discovered he had when operating on a blood clot behind his eye last Friday.

As a senator, McCain has access to high-quality health coverage, and he is being treated by a team at the Mayo Clinic Hospital in Phoenix, one of the best-regarded cancer treatment centers in the country. (For more information on this and other political stories, subscribe to the White House Patch to receive daily newsletters and breaking news alerts.)

Still, glioblastoma is an aggressive and fast-growing form of cancer that poses serious risks. Here's what you know about the cancer:

1. McCain's age is likely a factor in the disease.

At 80 years old, the Arizona Republican is much more susceptible to this type of cancer than a younger person. Glioblastomas represent around 15 percent of all brain cancers that affect humans, according to the American Brain Tumor Association, but only 3 percent of childhood brain tumors are caused by this form form of the disease.

Glioblastomas are also more likely to affect men than women.

2. The tumors can cause vision problems, memory impairments and speech difficulties.

Glioblastomas produce symptoms common in many diseases, including vomiting, loss of appetite, headache, nausea and muscle weakness. But depending on the location of the tumors in the brain, the cancer can also cause affect the mind, including vision problems, memory impairments and speech difficulties.

McCain drew attention during the recent testimony of former FBI Director James Comey when he asked a confusing and muddled series of questions. Comey struggled to answer the questions, and McCain's staff later blamed the incident on lack of sleep. The Washington Post suggests his unclear line of questioning could be linked to the speech difficulties glioblastoma can cause.

3. Glioblastoma is fast-growing and difficult to treat.

The cancer forms in the supportive tissues of the brain, according to the ABTA, and surgery is frequently required to relieve the pressure created by the tumors. However, because the disease multiplies quickly, excising the tumors will often leave residual cancer cells behind.

"Glioblastomas are usually highly malignant—a large number of tumor cells are reproducing at any given time, and they are nourished by an ample blood supply," ABTA writes. "Because gliblastomas have finger-like tentacles, they are very difficult to completely remove. This is particularly true when they are growing near the parts of the brain that control important functions such as language and coordination."

4. A multi-pronged treatment approach is usually required

Radiation therapy, chemotherapy and targeted drugs are all useful treatments in fighting glioblastoma in addition to surgery, according to the Cancer Treatment Centers of America. A multi-pronged approach is often demanded with this form of the disease because the tumors can contain multiple types of cancerous cells.

Targeted therapy zeros in on cancerous cells while ignoring normal cells.

"Targeted therapy can help when other treatments are not working as well," explains CTCA. "They can also have less-severe side effects than standard chemotherapy medicine."

5. On average, patients can expect to live around one to three years with treatment.

According to ABTA, the median survival time for patients diagnosed with glioblastoma is two or three years. Those with more aggressive forms of the disease have a median survival time of about 14 months.

And while removing the tumors is often recommended, they are very likely to recur.

"Unfortunately, the recurrence rate for glioblastomas is near 100%, with an average time to recurrence of six to seven months," says the MD Anderson Cancer Center.

Video: Colleagues Voice Support For John McCain After Brian Cancer Diagnosis

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