Swayze had planned to attend a TV Critics Association media event on Jan. 9 to talk about his A&E series "The Beast," but the actor told People magazine that he called his doctor and checked into the hospital because of a cough that wouldn't go away.
"It made me suspect there was a possibility of some kind of infection," he told the magazine. "I wanted to jump on it before it turned into a problem."
Swayze remains in the hospital but told People that he's "almost in the clear."
Dr. Harold Frucht of the Pancreatic Cancer Prevention and Genetics Program at Columbia University in New York City said the change in chemotherapy regimen that Swayze recently mentioned to Barbara Walters during his first interview since his cancer diagnosis is probably to blame.
"He mentioned that his chemo regimen was recently changed -- this would probably be about a month ago," Frucht said. "It is possible that the new chemo is causing a decrease in his WBC [white blood cell] count, which would predispose him to infections."
Swayze said that in the year since his diagnosis, he had defied the statistics and "trash magazines" that predicted he should have "already been dead a long time," but he acknowledged that time may be running out.
"I'd say five years is pretty wishful thinking," he told Walters. "Two years seems likely if you're going to believe statistics. I want to last until they find a cure, which means I'd better get a fire under it."
The 56-year-old actor said he's waging his battle against cancer "moment to moment."
"When do you decide the fight isn't matching up to your quality of life?" he asked. "So far, I've got potential for a lot of quality of life."
Swayze responded well to his first round of chemotherapy, but as is common, that treatment eventually became less effective, so he recently began a new therapy.
"You can bet that I'm going through hell," Swayze said, but he vowed to keep fighting.
"I'm at the beginning of my battle. And I expect it to be a long hard battle, one that I'm gonna win according to certain rules … the rules that the cancer isn't going away. Now, mind you, I keep my heart and my soul and my spirit open to miracles. I pray."
Asked if he was scared, Swayze told Walters, "I don't know. I will be so either truthful or stupid as to say no. But then I immediately, when I say that, I have to say yes, I am."
Swayze's battle with cancer began late in 2007. As he celebrated New Year's Eve with his wife, Lisa Niemi, Swayze felt that something was wrong.
"I tried to have champagne, and it would be like pouring acid, you know, on an open wound."
And soon it got worse.
"My indigestion issues got gigantic and constant. And then I started thinking, 'I'm getting skinny. I dropped about 20 pounds in the blink of an eye.' And then when you see it in the mirror, when all of a sudden you pull your eyes down and the bottom of your eyes go yellow and jaundice sets in -- then you know something's wrong."
Swayze realized that he needed medical attention. "I started doing a little research and started realizing this is not pretty. This is not a good thing."