Good Morning America anchor Robin Roberts will undergo chemotherapy and a bone marrow transplant, according to Roberts, who made the announcement this morning.

Roberts, who was diagnosed with breast cancer 5 years ago, has Myelodysplastic syndrome (MDS) a pre-leukemia blood disease caused by radiation.

Roberts, 51, underwent radiation therapy to kill the remaining cancer cells after a double mastectomy 5 years ago.

The bone marrow transplant will take place later this year, but Roberts will begin chemotherapy immediately. She will be off the show for an undetermined period of time after the bone marrow transplant. But Roberts hopes to keep working at GMA full time.

“My big sister is the perfect match for me, and she’s going to be my donor,” said an emotional Roberts as her sister looked on during this morning’s show.