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.
At seven years, the survival rate for these women drops to 11 percent.
These figures, however, are based on averages -- which means that with rapid and effective treatment, some patients can beat the odds.
"There are women who live with recurrent or metastatic breast cancer for many, many years," Winer said.
However, there may be more to worry about than a tumor in her rib.
Elizabeth Edwards' physician, Dr. Lisa Carey of the University of North Carolina's Lineberger Cancer Center, said during the press conference that Edwards has suspicious sites elsewhere in her body -- meaning that the cancer may not be only in her bone.
"In addition to the bone, it's possible that it's involving the lung," Carey said.
But one thing about Elizabeth Edwards' diagnosis is clear -- in all likelihood she will have her cancer for the rest of her life.
But the cancer may not necessarily mean a death sentence.
Once cancer has spread to other parts of the body, Winer says, treatment "is not curative, but it can help a woman live a long, long time."
Part of this treatment usually involves a different type of chemotherapy drug than was used in the first wave of efforts to fight off the cancer.
"It is also important to realize that we have more at our disposal than just chemotherapy," Winer adds, noting that newer, targeted therapies can often offer these women a better chance at fighting off cancer for a second time.