(Image source from: People)

A senior United State senator from Arizona John McCain, the maverick Republican who survived a Vietnam War prison camp and ran unsuccessfully for president, is discontinuing medical treatment for an aggressive form of brain cancer, his family has said in a statement, a year after he announced his diagnosis.

"John has surpassed expectations for his survival," the family said, adding the disease's progression and McCain's age, 81, had led him to stop treatment for the "aggressive glioblastoma".

"With his usual strength of will, he has now chosen to discontinue medical treatment," the family said.

The senator, who would turn 82 on August 29, has been away from the Capitol since December.

McCain, a former Navy pilot, was held as a prisoner of war in Vietnam for over five years, where he was tortured and left with lasting disabilities.

He was shot down during a bombing run over Hanoi and captured in 1967. The crash and assault by his captors left him with two broken arms, a broken leg, a broken shoulder and numerous stab wounds.

In the early 1980s, he was elected to Congress and was elected to the Senate in 1986. McCain has a reputation for speaking his mind, which led to a running feud with President Donald Trump.

The McCain-Trump relationship heated up in 2015 when McCain said Trump's candidacy had "fired up the crazies".

McCain rendered one of the most dramatic moments in recent Senate history in July 2017 when he voted against a Trump-backed bill that would have repealed the health care law pushed through by former president Barack Obama.

McCain's wife, Cindy, tweeted: "I love my husband with all of my heart. God bless everyone who has cared for my husband along this journey."

Trump was furious over McCain's vote and oftentimes referred to it at rallies but without mentioning McCain by name.

The chairman of the Senate Armed Services Committee, McCain, criticized Trump for his kudos of Russian President Vladimir Putin and some other foreign "tyrants" and lambasted Trump in The Restless Wave, an autobiography released in May.

Trump retorted that the senator was "not a war hero" and referred to McCain's years as a prisoner of the North Vietnamese by saying, "I like people who weren't captured".

Sources close to McCain said Trump would not be invited to the funeral.

McCain underwent surgery in July 2017 to take away a blood clot in his brain after being diagnosed with an aggressive tumor called a glioblastoma.

He rebounded speedily, however, returning to Washington and entering the Senate in late July to a standing ovation from his colleagues.

He later cast a crucial vote against the Republican health care bill, in a dramatic turn,  earning the fury of Trump, who oftentimes cites McCain's vote at campaign events.

McCain's condition worsened past fall and he has been in Arizona since December.

By Sowmya Sangam