Induction of molecular remission by donor peripheral blood leukocyte therapy in patients relapsing with extramedullary blastic phase chronic myeloid leukemia after allogeneic bone marrow transplantation.

Two patients with chronic myeloid leukemia (CML) who relapsed in blastic transformation after allogeneic bone marrow transplantation (BMT) were treated with infusions of leukapheresed peripheral blood mononuclear cells from their original donor. At relapse, their disease was characterized by symptomatic extramedullary deposits of leukemia with minimal (PCR positive, cytologically negative) involvement of bone marrow. Treatment with donor cell infusions was associated with clinical remission, return of full donor chimerism and loss of the BCR-ABL transcript detectable in bone marrow before donor leukocyte infusion (molecular remission). Donor leukocyte infusions should be considered for therapy of relapsed blastic phase CML after allogeneic BMT, especially when the relapse is primarily extramedullary and responsive to local and systemic cytoreductive therapy. However, severe GVHD and CNS relapse remain obstacles to achieving a successful long-term outcome.