Dose dependent long-term in vivo remission of AML1/ETO positive acute myeloid leukemia with G-CSF

In addition to the ability of G-CSF to stimulate the maturation and function of granulocytes, experimental and clinical evidence suggests that induction of leukemia cell differentiation may also be possible. This critical effect has received little attention with respect to its potential therapeutic application in myeloid malignancies. We describe the clinical course of a 62-year-old patient with atypical AML1/ETO-positive AML-M2 who repeatedly displayed a marked, dose-dependent response to G-CSF. He was originally investigated for neutropenia, but declined chemotherapy at diagnosis of AML (40% bone marrow blasts) and commenced G-CSF therapy when a life-threatening chest infection occurred. The bone marrow infiltration regressed and his blood counts normalized after 20 days. A slow relapse occurred over the next 3 months but a second hematological remission was achieved upon reintroduction of G-CSF. He remained well and free of transfusions for 2.5 years, receiving only maintenance G-CSF. Despite the presence of the AML1/ETO transcript, his leukemic blasts always failed to demonstrate the typical morphological, immunological and cytogenetic characteristics of AML1/ETO-AML of M2 subtype. He eventually developed resistance to G-CSF and died from sepsis after cytotoxic therapy. In selected AML cases differentiation therapy with growth factors may emerge as a useful antileukemic strategy, either alone or as an adjunct to established treatment modalities.