Chapel Hill, N.C. — Presidential hopeful John Edwards announced Thursday that his wife's cancer had returned, but he has no plans to stop campaigning.

Elizabeth Edwards said she recently cracked a rib, and an X-ray showed a suspicious spot on her right side, which a biopsy determined to be cancer. Medical tests also showed spots on one of her lungs, but doctors haven't determined whether they also indicate cancer.

Since her breast cancer had moved into bone, the cancer is no longer curable but can be treated, said Dr. Lisa Carey, an oncologist at the University of North Carolina's Lineberger Comprehensive Cancer Center.

One in five breast cancer patients suffers a recurrence of the disease, Carey said. The five-year survival rate for people with such Stage 4 cancers is 26 percent, according to the American Cancer Society.

"I don't look sickly, I don't feel sickly. I am as ready as any person can be for that," Elizabeth Edwards said at a news conference. "We're always going to look for the silver lining. That's who we are as people."

John Edwards, a former U.S. senator from North Carolina, cut short a campaign trip to Iowa to be with his wife. He still attended a barbecue fundraiser Wednesday evening in Chapel Hill.

Trying to focus on his wife's health and his campaign is no different than the challenges a president faces on a daily basis, he said. But he made it clear his top priority would be her health.

"We will be in this every step of the way together," he said. "Anytime, anyplace I need to be with Elizabeth, I will be there."

Elizabeth Edwards said she encouraged her husband to remain in the 2008 presidential race, saying other people face more hardship than she does and need his leadership.

"It's important that the American people have a president like him. I can't deprive them of that," she said.

As she undergoes chemotherapy, she said, she occasionally will have to pull back from the campaign to regain her energy. Still, she said she expects her life to change little.

"I expect to do next week everything I did last week, and the next week and next year at the same time," she said.

The couple will campaign together in California Friday before heading to a forum in Las Vegas over the weekend.

Initial Diagnosis in 2004

Elizabeth Edwards, 57, first discovered a lump in her breast in the final days of the 2004 campaign, when her husband was the Democratic vice presidential nominee. He announced the diagnosis the day after he and presidential nominee John Kerry lost the election to President George W. Bush.

She was diagnosed with invasive ductal cancer, the most common type of breast cancer. It can spread from the milk ducts to other parts of the breast and beyond. She wrote about her life, including her breast cancer treatment, in a book published last year called "Saving Graces." She had surgery and underwent several months of radiation and chemotherapy.

John Edwards delayed entering the 2008 race until he was certain her cancer was in remission. He announced his candidacy in December in New Orleans.

He has registered double digits in public opinion polls and is considered a top-tier candidate for the Democratic nomination, although he trails front-runners Hillary Rodham Clinton and Barack Obama.

Elizabeth Edwards said she was lifting a heavy chest at the couple's Chapel Hill home recently and strained her back. Later, she said, she pulled away from her husband's embrace to protect her injured back and cracked a rib.

She called the sequence of events "a blessing" since it led to the X-ray that discovered her recurrence of cancer.

"It's lucky I cracked a rib," she said with a laugh.

Carey, the oncologist, said it's too early to determine the course of Elizabeth Edwards' treatment. But she noted there are a number of drugs that are effective against the cancer.

"We don't know what's going to happen with Mrs. Edwards. But we do know that there are effective treatments and that she looks good," Carey said.

After getting the diagnosis this week, the couple spent a day notifying relatives and discussing the situation with their children.

"We're very optimistic," John Edwards said. "We've been through struggles before, and we know the key is to keep your head up, keep moving and stay strong."