A source close to McCain who asked not to be identified said Friday the senator was at his Arizona ranch with his family.
"They have decided not to extend any other options to him for treatment because at some point, the risks outweigh the benefits".
"The progress of disease and the inexorable advance of age render their verdict", the 81-year-old senator's loved ones said in a statement.
McCain with his fighter squadron in 1965. He was severely injured and spent more than five years as a prisoner of war. But he was also left with permanent physical disabilities and deep emotional scars.
He was elected to the House of Representatives in 1982 and the Senate in 1986. He had suffered from a malignant brain tumor, called a glioblastoma, for which he had been treated periodically with radiation and chemotherapy since its discovery in 2017.
He ran unsuccessfully for the Republican presidential nomination in 2000, then won it in 2008.
The allusion to the medical deferment that saved a young Donald Trump from serving in that war could not have been clearer.
If McCain should resign his seat or die soon, Republican Arizona Gov. Doug Ducey would name a replacement to serve until the 2020 election.
India vs England 4th Test Day 1 live updates
The Ageas Bowl track had a decent covering of grass is expected to have more bounce than the previous venues of the series. Jasprit Bumrah (left) celebrates the wicket of Jonny Bairstow on the first day of the fourth Test at Southampton .
But Trump was not the only GOP president to feel the wrath of McCain's vengeance.
"Today's press conference in Helsinki was one of the most disgraceful performances by an American president in memory", McCain said in a blistering statement.
McCain announced that he would instead vote for "some good conservative Republican who is qualified to be president". He stunned the GOP by actively considering an offer from the Democrat presidential challenger in 2004, John Kerry, to join his ticket.
In more than three decades in Congress, McCain became known as a political maverick willing to stick to his convictions rather than go along with party leaders - an independent streak that has drawn a mix of respect and ire. Although he and I sometimes disagreed, I was deeply privileged to serve with him and proud to call him a friend. And of course, his major legislative accomplishment was co-sponsoring with liberal Sen.
But it was McCain's fortitude after joining the Navy that would define him.
McCain with running mate Sarah Palin during unsuccessful 2008 presidential campaign. Before his death, he was the "chairman of the Senate Committee on Armed Services, a member of the Senate Committee on Indian Affairs and a member of the Senate Committee on Homeland Security and Governmental Affairs", according to People Magazine. Along with his longtime friend, the equally camera-friendly Lindsey Graham (R-SC), McCain was a persistent advocate for increased defense spending and aggressive USA military action.
McCain was married to Carol Shepp from 1965 until 1980, when the two divorced and he married his second wife, Cindy Hensley. Heidi and I send our heartfelt thoughts and prayers to Cindy, and to the entire McCain family, as they grieve the loss of a loving husband, father, and grandfather. His legacy as a significant political figure who bridged the gap from the 20th to 21st century is secure.
John McCain was a battler to the end, a man who survived a captivity that would break most men, thrived on his own terms in the Washington swamp and was defiant in the face of a fatal illness.