Elizabeth Edwards Enters Second Cancer Fight

March 22, 2007— -- More than two years after her first bout with cancer, Elizabeth Edwards, wife of Democratic presidential hopeful John Edwards, is entering round two of her fight against the disease.

"The bottom line is her cancer is back," John Edwards said in a press conference Thursday. "We are very optimistic about this because, having been through some struggles together in the past, we know, the key is to keep your head up."

However, with the most recent case of cancer already in stage IV, the Edwardses could be facing some difficult odds.

According to the Mayo Clinic, cancer recurrence happens when cancer cells are left over after treatment of an initial cancer. Though the recurrence can happen in the same area as the original cancer, it can also arise in other parts of the body.

In Elizabeth Edwards' case, the remnants of her first cancer apparently spread from the soft tissue of her breast into the solid tissue of her right rib.

At the time of her first cancer treatment, doctors believed that the cancer had not spread to any other parts of her body. Edwards had undergone chemotherapy, surgery and radiation between 2004 and 2005 to get rid of her first breast tumor, which was about the size of a half-dollar.

However, a recent X-ray on a fractured rib on her left side revealed a suspicious growth on her right side. A biopsy later revealed this to be a small tumor in her bone -- a recurrence of her original cancer from two years ago.

"Recurrence can take a number of different forms," Dr. Eric Winer, director of the Breast Oncology Center at Dana-Farber Cancer Institute in Boston, told ABC News Now's "Healthy Life" program.

Once the cancer appears in bone, it is considered incurable, but doctors say she still could have years to live.

"It is now incurable in a technical sense, but treatable," ABC News' medical editor Dr. Tim Johnson said. "Many women will survive many years under this scenario with new modern effective treatments."

Stage IV refers to a cancer that is metastatic, meaning that it has spread from its original site into other parts of the body.

According to the American Cancer Society, there are no reliable statistics on the survival of women with recurrent stage IV breast cancer.

However, women with an initial diagnosis of stage IV breast cancer have a five-year survival rate of between 18 and 20 percent. This means that for every five women who have stage IV breast cancer, only one survives after five years.