Reinduction of relapsed acute promyelocytic leukemia with ATRA and low dose antimetabolite-based chemotherapy.

While the disease-free survival of acute promyelocytic leukemia (APML) now approaches 75%, some children continue to experience relapses, and questions remain as to the optimal management of these patients. We describe two young children who experienced combined relapses in the bone marrow and extramedullary locations following hematopoietic stem cell transplantation (HSCT). An induction regimen, consisting of all-trans retinoic acid (ATRA), methotrexate, and 6-mercaptopurine (6MP), successfully and safely achieved hematologic remission in one patient and molecular remission in the other. These cases demonstrate that there is a role for ATRA plus differentiating chemotherapy other than arsenic trioxide in the treatment of relapsed APML.