Farrah's Story, a two-hour documentary about actress Farrah Fawcett's battle with cancer, will air on NBC on Friday. (Rene Macura/Associated Press)

Next Friday, a two-hour documentary, Farrah's Story, shot by actress Farrah Fawcett and her friend Alana Stewart about Fawcett's battle with cancer, will air on NBC.

Fawcett, 62, who was diagnosed with anal cancer 2½ years ago, said she believes others may benefit from learning about her experience with the disease.

"This film is very personal," she says in one of the clips in the film. "But at some point, the footage took on a life of its own and dictated that it be seen."

Her longtime partner, actor Ryan O'Neal, said in an interview in the current issue of People magazine that Fawcett is losing her battle with cancer.

After her initial diagnosis, the star of the former Charlie's Angels television series had surgery to remove a tumour and chemotherapy. But the cancer returned in 2007 and O'Neal said it has now spread to other parts of her body, including her liver.

"She stays in bed now," he said. "The doctors see she is comfortable. The treatment is pretty much ended."

Fawcett has lost her famous mane of blonde hair, he added.

"It's a love story," said O'Neal, 68, who played opposite Ali McGraw's terminally ill character in the 1970 film Love Story. "I just don't know how to play this one. I won't know this world without her."

Last month, Fawcett received a supervised visit from Redmond O'Neal, her 24-year-old son with Ryan O'Neal. He was released from custody to visit his ailing mother and has subsequently been placed in an intensive drug rehabilitation program for possession of narcotics.