John McCain's Brain Cancer: Here's What You Need to Know

While early detection for all cancers is important, a diagnosis of glioblastoma — the deadliest form of brain cancer — is always bad news.

While early detection for all cancers is important, a diagnosis of glioblastoma — the deadliest form of brain cancer — is always bad news. Fewer than 5 percent of glioblastoma patients live more than 5 years after being diagnosed. No new treatments in recent years have proved effective at containing it.

McCain, who receives federal taxpayer-funded health insurance as a member of Congress, has a difficult road ahead of him. It doesn’t matter if you’re a war hero or a senator or a vice president’s son (both Senator Ted Kennedy and Beau Biden died from the same disease), it’s a grim prognosis.

Glioblastomas are a type of glioma, a broad category encompassing any tumor that starts in glial cells, the most common cells in the brain. Gliomas account for about 33 percent of all brain tumors, and glioblastomas (also known as grade IV astrocytoma tumors) are the most malignant of all of them. The American Brain Tumor Association (ABTA) estimates that about 12,000 people are diagnosed with glioblastomas yearly.

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There are no definitive risk factors known for glioblastomas, although they have been linked to radiation exposure. They are most common in older, white men.

One of the things that makes glioblastomas so pernicious is that their cells multiply rapidly and invade surrounding brain tissue, intertwining themselves with normal brain cells. This makes them almost impossible to completely remove with surgery, and allows them to continue to grow even if the bulk of the original tumor is removed. Researchers have found that it only takes about seven months after surgery for glioblastomas to recur.

They are also unique in other ways. Many solid tumors have their own vasculature — a jumbled network of blood vessels that supply the tumor with the oxygen and nutrients it needs to grow. But glioblastomas are especially highly vascularized, which is partly how they are able to grow so quickly.

Glioblastomas are also made up of a mosaic of diverse cells. Many if not all glioblastoma cells have a different genetic makeup, making it impossible to find one common mutation or target for treatments. Even if a therapy was able to kill one type of tumor cell, the others would still live and continue to grow.

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Once the glioblastoma begins to grow, symptoms will come soon after. According to the ABTA, the most common glioblastoma symptoms include increased pressure in the brain, dizziness, seizures, headache, nausea, and drowsiness. In the wake of his diagnosis, some people have wondered if McCain’s glioblastoma might have contributed to his bizarre and confusing line of questioning of James Comey last month before the Senate Intelligence Committee.

McCain hasn’t yet indicated what treatment he will pursue for the brain tumor. Much of it has already been surgically removed, but that will not be enough. The average life expectancy for people diagnosed with glioblastoma ranges between 12 and 14 months. Though there are many potential treatments in the pipeline, it seems unlikely that any of them will be useful for McCain.

Among his options, McCain might decide to get radiation treatment soon. But even radiation will likely only give him a few extra months. Either way, this aggressive brain tumor won’t stay down for long. War hero or no, cancer refuses to discriminate.

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