She was treated for breast cancer after the 2004 presidential campaign.
Mr Edwards is a former US senator from North Carolina and the 2004 Democratic vice presidential nominee.
Mr Edwards said on Thursday he would continue his 2008 presidential campaign. He is running third in national polls behind Senators Hillary Rodham Clinton of New York and Barack Obama of Illinois.
Mr Edwards announced his wife’s breast cancer the day after he and Senator John Kerry lost the 2004 election to President George Bush.
She underwent months of radiation and chemotherapy, and wrote about her experiences last year in a book called “Saving Graces.
The Edwards met while they were law students and married in 1977. Their first child, Wade, was killed in a 1996 car crash; they have three surviving children.
Mr Edwards, 53, said on Thursday that a biopsy had shown that his wife had cancer in the bone on a rib on her right-hand side. He said the disease was incurable, but treatable.
