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en. John McCain has been diagnosed with the aggressive brain cancer glioblastoma, his office said on Wednesday. McCain had undergone surgery to remove a blood clot above his left eye last week, and a subsequent pathology report of that tissue found that it was cancerous.

“The Senator and his family are reviewing further treatment options with his Mayo Clinic care team,” his office said in a written statement.

Here are five things to know about glioblastoma and McCain’s future health.

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What is glioblastoma?

Glioblastoma is the most common form of brain cancer, making up 16 percent of all brain malignancies. It is rare, striking some 3 people out of 100,000 in the U.S. (there will be an estimated 13,000 new cases this year), more men than women, and more whites than people of other races. The only known cause is ionizing radiation including that received for another tumor (McCain is not known to have had such therapy), though some studies have suggested an increased risk from some pesticides and petroleum products. Glioblastoma is also very aggressive, so much so that surgery almost never produces a cure; by the time it is diagnosed glioblastoma has almost always spread to multiple regions of the brain that cannot be reached through surgery. Virtually unique among cancers, however, glioblastomas do not spread to organs beyond the brain such as the lungs or bones, for reasons scientists do not understand.

Is it related to McCain’s previous cancers?

McCain has had multiple cases of melanoma, a skin cancer, that have been removed surgically according to health records he made public during his 2008 presidential bid. However McCain’s glioblastoma is a primary tumor, doctors said in the note issued by his office, meaning that it arose independently of those previous bouts of cancer.

What treatments come next?

According to the note from McCain’s physicians, “treatment options may include a combination of chemotherapy and radiation.” But it’s not clear yet what the timetable is for those treatments. For now, McCain is home in Arizona. “Further consultations with Senator McCain’s Mayo Clinic care team will indicate when he will return to the United States Senate,” his office said in a statement.

What’s the prognosis?

Not good. After undergoing surgery, radiation, and chemotherapy, some 70 percent of patients suffer further spread of their glioblastoma along with such serious side effects as cognitive decline and strokes. In a statement, McCain’s physicians said that “the tissue of concern was completely resected by imaging criteria,” meaning that when they performed the procedure to remove a blood clot above his left eye last week they got everything that was visible. Unfortunately, “micro-metastases” — just a few malignant cells that spread from the initial tumor — cannot be seen on CT or MRI scans, and “surgery alone is never curative for this disease,” said Dr. David Reardon, head of neuro-oncology at Boston’s Dana-Farber Cancer Institute. Barely 5 percent of patients with glioblastoma are alive after five years, and only half make it past 15 months. Reardon cared for Sen. Edward Kennedy of Massachusetts, who was diagnosed with glioblastoma in May 2008 and died in August 2009.

Are there any experimental treatments on the horizon?

Yes: some 157 clinical trials in the U.S. are testing experimental treatments on adults with glioblastoma. In one promising approach, scientists at Dana-Farber are creating personalized cancer vaccines that target the specific molecules on a single patient’s tumor; the vaccine triggers the immune system to attack those molecules, and hence the tumor, an approach that produced encouraging results when it was recently tried in melanoma.

Personalized cancer vaccines rally the immune system to identify and kill cancerous cells based on genetic information from the patient's own tumors. Alex Hogan, Hyacinth Empinado/STAT

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  • How can this cancer be simultaneously “the most common form of brain cancer….16%” , and rare ” striking 3 out of 100,000 cases”? I believe it to be rare and difficult to treat. God bless John McCain and his doctors.

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