This is a very aggressive cancer, and typical survival rate after diagnosis is around a year and a half:

Sen. John McCain (R-Ariz.) has been diagnosed with a brain tumor, his office said Wednesday, throwing into doubt when and if he will return to Washington to resume his duties in the Senate.

The Mayo Clinic said doctors diagnosed a tumor called a glioblastoma after surgery to remove a blood clot above McCain’s left eye last week. The senator and his family are considering treatment options, including a combination of chemotherapy and radiation, according to the hospital.

McCain, 80, has been away from the Senate this week, recovering from the surgery and undergoing tests. His office issued a statement describing him “in good spirits” and noting that his doctors say his underlying health is excellent — but not indicating when he will return to the Senate.

Glioblastoma is an aggressive type of brain cancer, and the prognosis for this kind of cancer is generally poor. Sen. Edward M. Kennedy (D-Mass.) survived less than 15 months after his was found in 2008. McCain’s doctors said the “tissue of concern” was removed during the blood-clot procedure.

In the best case, McCain is unlikely to be back in Washington for a while, which would make things even worse for Mitch McConnell in his attempts to corral votes.