Sen. John McCain, R-Ariz., has decided to stop medical treatment for glioblastoma, a rare form of brain cancer, the McCain family announced in a statement Friday.

“Last summer, Sen. John McCain shared with Americans the news our family already knew: he had been diagnosed with an aggressive glioblastoma, and the prognosis was serious. In the year since, John has surpassed expectations for his survival. But the progress of disease and the inexorable advance of age render their verdict,” the McCain family said.