It's so rare, doctors say, that many caregivers don't routinelyscreen for it and many patients don't notice it until it reachesadvanced stages.
"Early on, the patient often doesn't feel anything or knowanything," said Dr. Michael Hellinger, colorectal surgeon at Mt.Sinai Hospital in Miami Beach. "As it advances, with rectal bleeding,a little lump, people sometimes think it's hemorrhoids."
That's tragic, because when anal cancer is caught early, before ithas spread to lymph nodes, liver or lungs, the five-year survival rateis 82 percent, according to the American Cancer Society.
The survival rate drops to 60 percent if it has spread tosurrounding lymph nodes, 20 percent if it spreads to lungs, liver orother organs. The anus is the opening at the lower end of thedigestive tract through which solid waste is excreted. Above it is therectum, then the colon.
Among patients under 50, anal cancer is more common in men; after50, it is more common in women. It occurs more often in smokers,people who have many sexual partners, have receptive anal intercourseor have a weakened immune system, the American Cancer Society says.
Some doctors believe that means it's more common among men who havesex with men and have anal intercourse, Hellinger says. "But that'snever been statistically proven. Studies have never been done to lookat that."
Another cause can be chronic infection with the human papillomavirus, in both men and women. HPV can be spread by either straight orgay sex, Hellinger said. And while it can be slowed among women whotake the HPV vaccine to avoid cervical cancer, the vaccine never hasbeen studied in men, and men are not routinely vaccinated.
When anal cancer is diagnosed, the standard care is chemotherapyand radiation. Until the 1970s the standard treatment was a "radicalabdominal perineal resection," Hellinger said, in which the entirerectum and anal canal are removed, requiring the patient to wear anexternal colostomy bag.
In her TV program, "Farrah's Story," videotaped by Fawcett andher friends and broadcast on NBC on May 15, she made two statementsthat have led some to question her decisions about her own care.
First, she says her UCLA doctors wanted to do the radical surgeryafter the cancer had spread to her lymph nodes and liver. Instead, shetraveled to Germany and found a surgeon willing to remove the tumorwithout the wider operation.
Second, until the final months, she insisted that any chemotherapyshe was given involved drugs that would not cause her famous hair tofall out.
Hellinger declined to speculate on those decisions.
"It's impossible to judge without more information," he said.