Good Morning America anchor Robin Roberts has fought–and won–the battle against breast cancer, and now she’s having to face a much more painful foe: MDA, or myelodysplastic syndrome.

She announced the news today via a letter to her fans and says she is confident she will beat it, because doctors assure her she is young and fit enough to battle through it. She’s also fortunate enough to have a sister who is an excellent match for bone marrow, and she will undergo a transplant later this year. For now, she’ll start chemotherapy.

Roberts writes, “Today, I will start what is known as pre-treatment -– chemotherapy in advance of a bone marrow transplant later this year. Bone marrow donors are scarce and particularly for African-American women. I am very fortunate to have a sister who is an excellent match, and this greatly improves my chances for a cure. As you know from my recent interview with Mark Zuckerberg, organ donation is vitally important. Many people don’t realize they can be bone marrow donors. I encourage everyone to sign up on a donor registry like bethematch.org.”

The treatment for cancer often comes with high risks, such as a heightened probability to develop other diseases. Roberts will have a long and painful road to recovery ahead of her, but insists she will still anchor GMA throughout the process.