Last month, Carter wrote an op-ed in the New York Daily News, in which he revealed to readers that he is "quite literally" on his deathbed.
Today, the former professional middleweight boxer weighs just 70 pounds.
At Carter’s Toronto home, John Artis has been watching over his ailing friend for the past two years.
Nearly five decades ago, Artis and Carter were each wrongfully convicted in a triple murder in Paterson, New Jersey.
Artis spent 15 years in prison as a result, and Carter nearly 20 years, before they were exonerated.
"I was there, kind of like in the beginning you could say, so I might as well be here with him at the end," Artis told CBC News in an interview on Tuesday.
In the years that followed, the story of Carter’s wrongful conviction and fight to clear his name would be told in books, a famous song co-written by Bob Dylan and eventually a movie, 1999's The Hurricane, which starred Denzel Washington and was directed by Norman Jewison.
"He’s fighting arduously to live, but that’s his will to live,” Artis said. “But the disease, the cancer, is taking a mighty toll on him."
While Carter’s own fight may be nearly over, he has one last wish that he hopes will come true.
Carter is pushing for U.S. authorities to take another look at the case of David McCallum.
He believes that McCallum was wrongfully convicted in a Brooklyn, N.Y., murder 29 years ago and that authorities should give him a full hearing.
"He would really, really, really sincerely like to see this guy released," said Artis.
Artis said Carter has pored over McCallum’s case and is convinced he is innocent.
"Having been wrongfully accused ourselves, you know, it’s sort of like an enemy to him," Artis said. "And it’s a war that has to be fought and he’s not afraid to get out on the front line."