Relapse occurs most often in the bone marrow but may also happen in the CNS or testes. Bone marrow relapse is an ominous event. Although remissions can be reinduced in 80 to 90% of patients, subsequent remission tend to be brief, and patients usually have already been exposed to the most effective drugs.
While the majority of children with recurrent ALL attain a second remission, the likelihood of cure is generally poor, particularly for those with bone marrow relapse following a short initial remission duration.