Graft-versus-leukemia effect on infant lymphoblastic leukemia relapsed after sibling hematopoietic stem cell...

Infant acute lymphoblastic leukemia (ALL) is considered a high-risk entity. Patients diagnosed in the first 3 months of life have especially high mortality. By morphology, infant ALL is classified as a lymphoid lineage leukemia; however, its physiologic behavior has brought many to consider it a pathologic hybrid between lymphoid leukemia and myeloid leukemias. As such, standard of care currently employs the use of chemotherapeutic agents used commonly in ALL protocols and agents typically reserved for the treatment of myelogenous lineage leukemias. The role of hematopoietic stem cell transplantation and graft-versus-leukemia effect in these patients has not been well studied.

An earlier healthy 9-week-old Hispanic male diagnosed with precursor B-cell lymphoblastic leukemia was treated with protocol P9407 and matched sibling hematopoietic stem cell transplantation. Relapse was noted on posttransplant day +114 with blasts on peripheral blood smear. The sole antigraft-versus-host disease (GVHD) agent, cyclosporine, was discontinued. Blast clearance from the peripheral blood was obtained by posttransplant day +128 with the appearance of skin and liver GVHD at posttransplant day +181. Bone marrow examination on posttransplant day +205 revealed normal marrow with no evidence of leukemic cells. He remains disease free more than 2 years posttransplant.

Traditionally, graft-versus-leukemia effect was thought to contribute therapeutically little to the treatment of ALL by hematopoietic stem cell transplantation (HSCT). The effects of graft-versus-leukemia immunologic phenomenon in our patient with infant acute lymphoblastic leukemia underscore the potential that infant ALL may not be entirely the same biologic entity as standard pediatric ALL and may be more responsive than understood earlier. Therapeutic response and appearance of GVHD after the withdrawal of immunosuppression in this patient provides evidence that graft-versus-leukemia effect may play a role in disease control in infant ALL after HSCT. Patients who relapse after the HSCT may be salvaged with the withdrawal of immunosuppression. This suggests that other immunotherapeutic interventions in the context of relapse may offer potential clinical benefit in this disease.