Successful repeated treatment of acute myeloid leukemia in early relapse with gemtuzumab ozogamicin alone.

A 68-year-old female was diagnosed with acute myeloid leukemia (AML-M2 without 8/21 translocation) in December 2006. Although a complete remission (CR) was obtained after induction chemotherapy, the first post-remission therapy was discontinued because of severe cardiovascular complications. She had a relapse of AML with CD33-positive myeloblasts which comprised 38.4 % of the bone marrow cells in November 2007. She received two courses of low-dose chemotherapy because of the previous complications. The amount of Wilm's tumor 1 (WT1) mRNA in the peripheral blood was 13,000 copies/μg RNA after the first course of the chemotherapy, and 4.8 % myeloblasts remained in the bone marrow after the second course. She was treated with a single course of gemtuzumab ozogamicin (GO), with a subsequent CR with 0.9 % marrow myeloblasts and fewer than 50 copies of WT-1 mRNA (normal level). Thereafter, she received five courses of GO monotherapy at each occasion of early AML relapse. Hematological remission has been sustained over a period of about 24 months with the GO monotherapy alone. This case suggests that GO monotherapy is a useful salvage therapy for early relapse of CD33-positive AML in situations in which standard chemotherapy is not indicated.