Val Kilmer shocked fans with his frail appearance and ravaged voice as he struggled his way through a Feb. 9 speaking engagement in Los Angeles.
Barley able to speak, the dramatically thinner Batman Forever star strained his way through a presentation of his film Citizen Twain.
Fans struggled to understand Kilmer, who has repeatedly denied he has cancer, as he tried to explain his motivations for writing the one-man show, which he performed in 2013.
"He performs as the ghost of Mark Twain in the show, but even as a dead man he looked ten times better than he does now," one attendee told RadarOnline.com. "The difference between Val three years ago and him on stage now is both shocking and heartbreaking."
"He could barely stand, he had to sit down to talk," continued the attendee. "He was gasping for breath and he's lost about half his body weight. His face has such deep lines on it and he appears so fragile. It is so sad to see such a huge talent so humbled."
Kilmer, 57, initially denied developing a tumor in his throat and undergoing surgery to have it removed, but later confirmed that was the case.
He now claims to be completely healthy apart from a swollen tongue, but health experts and friends have indicated otherwise.
Kilmer is also a devout Christian Scientist, a religious system which believes diseases can be cured by prayer.
The actor's Citizen Twain show features many ruminations on God and death, and Kilmer says it took him 13 years to put together, leaving some wondering if it may be his swan song.
A fan explained: "The first half of the show is very funny, but the second half is a lot more reflective. It's very philosophical in places and deals with some big questions."
Meanwhile medical professionals have urged the star to seek more treatment for his ailing health before its too late.
"He is obviously in a dire situation," warned Dr. Otto Placik, who has not treated the star. "It's hard to tell how much time he has. My guess is that it's not very long-term."
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