How often does a bone marrow transplant not get rid of the leukemia?

Depends: The type of leukemia (acute vs chronic, myeloid vs lymphoid), the type of bone marrow transplant (allogeneic vs autologous), the status of the leukemia (complete remission, first remission, second remission, partial remission, etc.) all affect the success of a bone marrow transplant.

Variable: The success rate of a transplant is dependent on many factors: the type of leukemia, some genetic factors about the leukemia, current remission status, prior therapies, type of transplant and other medical problems of the patient.