Sen. John McCain Has Brain Tumor

In McCain's case, the senator and former presidential candidate showed no neurological problems before or after the operation, his doctors told CNN. The clot was discovered during a routine physical exam. Blood clots, however, are not one of the most common symptoms at diagnosis, Willmarth says. McCain also reported feeling fatigued and having brain fog as well as intermittent double vision, which prompted a CT scan. 

Treatment options vary

As with many tumor types, the exact cause of glioblastoma is not known. Treatment may combine several approaches because the tumors contain so many different types of cells. Certain therapies may work for some cells, but others may not be affected at all.

"The first step in treating glioblastoma is a procedure to make a diagnosis, relieve pressure on the brain, and safely remove as much tumor as possible through surgery," according to ABTA's website. "Because glioblastomas 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."

Radiation and chemotherapy may be used to slow the growth of tumors that cannot be removed with surgery. Mayo Clinic doctors who are involved in McCain's care told CNN that a minimally invasive craniotomy was performed. Postsurgical brain scans show that the tissue causing concern has been completely removed, and the senator has shown no neurological problems. He would need to heal from his surgery before beginning radiation.

McCain's condition is the same one suffered by his former colleague Massachusetts Sen. Ted Kennedy, as well as film critic Gene Siskel. Both men died from complications related to the tumor. Median survival is about 15 months, and about 10 percent of patients may live five years or longer, Willmarth says. ABTA offers resources to help patients through their journey, including navigating second opinions, finding clinical trials and treatment options, and supporting caregivers and patients throughout their experience.