51-year-old Roberts just released a statement saying, "Today, I want to let you know that I’ve been diagnosed with MDS or myelodysplastic syndrome. It's a disease of the blood and bone marrow and was once known as preleukemia."
She explains, "As many of you know, 5 years ago I beat breast cancer. I’ve always been a fighter, and with all of your prayers and support, a winner. Sometimes the treatment for cancer can cause other serious medical problems."
"My doctors tell me I'm going to beat this -- and I know it's true."
Roberts says she will begin pre-treatment starting today -- chemotherapy in advance of a bone marrow transplant later this year.
Roberts adds, "Bottom line: I’ve been living with this diagnosis for awhile and will continue to anchor GMA. I love what I do and the people with whom I do it. Along with my faith, family and friends, all of you at ABC News give me the motivation and energy to face this challenge."