The family of longtime Sen. John McCain, R-Ariz, said Friday that he has chosen to discontinue medical treatment for brain cancer. McCain, 81, was first diagnosed with the disease in the summer of 2017.
"I love my husband with all of my heart," his wife, Cindy McCain, wrote Friday, in a tweet accompanying the news. "God bless everyone who has cared for my husband along this journey."
McCain's daughter, Meghan McCain, also posted a tweet: "My family is deeply appreciative of all the love and generosity you have shown us during this past year. Thank you for all your continued support and prayers. We could not have made it this far without you - you've given us strength to carry on," she wrote.
Read the family's statement:
Last summer, Senator 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. 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.
The news of McCain's decision, while not entirely unexpected, was met with deep sadness from his Senate colleagues on Friday.
"Becoming John McCain's friend has been one of the great blessings of my life," former Sen. Joe Lieberman, one of McCain's closest friends, told CNBC in a statement. "Today I am praying for him and his family."
Few legislators in American history have served for more years, or in more capacities than McCain has during a Senate career that began in 1987 and lasted more than three decades. At various points during his tenure, McCain has chaired the Armed Services Committee, the Indian Affairs Committee and the Senate Commerce Committee.
McCain first garnered national attention during the Vietnam War, when, as the son of an admiral in the U.S. Navy, he spent more than five years as a prisoner of war, an ordeal that left him unable to lift his arms above his head.
McCain would go on to become an unparalleled advocate for POWs in Congress, and a staunch believer in the central importance of the Geneva Convention and the laws of war. Upon learning the news of his failing health, his fellow Vietnam veteran and former Senate colleague, John Kerry, wrote "God bless John McCain, his family, and all who love him — a brave man showing us once again what the words grace and grit really mean."
At the activation of a new Army command in Austin, Texas on Friday, Senate Majority Whip John Cornyn lamented that McCain could not be there because "he was key as the chairman of the Armed Services Committee in the Senate."
"I know he would love to be here and be pleased so my thoughts are with him and his family," the Texas Republican said.
McCain is also beloved by his current and former staffers, and many of the alumni from his office still work in jobs all over Capitol Hill. One of his longtime political strategists, John Weaver, reacted to the news Friday with sentiments shared by many who have worked for the senator.
CNBC's Brian Schwartz and Amanda Macias contributed to this article.