Sen. John McCain, 81, who announced his brain cancer diagnosis last summer, has discontinued his cancer treatment.

His office announced the news on Friday morning.

The Arizona senator has been away from Washington and back in his home state for months. He has been receiving treatment for aggressive glioblastoma.

“The progress of disease and the inexorable advance of age render their verdict,” his family said. “With his usual strength of will, he has now chosen to discontinue medical treatment.”

“Our family is immensely grateful for the support and kindness of all his caregivers over the last year, and for the continuing outpouring of concern and affection from John’s many friends and associates, and the many thousands of people who are keeping him in their prayers. God bless and thank you all.”

When McCain dies, Arizona Gov. Doug Ducey, a Republican, will appoint a replacement to serve in the Senate until 2020.