Reversible leukaemic regrowth under GM-CSF treatment after chemotherapy for AML

A 78-year-old woman with acute myelogenic leukaemia (AML M5 (FAB)) was treated with standard induction chemotherapy followed by recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) (250 micrograms/m2/day) in an effort to accelerate neutrophil recovery. After 10 days of rhGM-CSF therapy, increasing numbers of promonocytes and monocytes were detected in the peripheral blood, with a maximum total white blood count of 14,900/microliters of which 39% were promonocytes, 39% monocytes, and only 3% neutrophils. The bone marrow during GM-CSF therapy was hypercellular and contained 95% monocytic forms. After discontinuation of rhGM-CSF, this monocyte lineage stimulation was completely reversible. Without further chemotherapy the patient entered a complete remission after 9 months and is now relapse free after 24 months. Since the stimulation was restricted to the previously leukaemic lineage of this patient, the profound monocytosis observed in this case suggests the possibility that GM-CSF may exert reversible effects on the proliferation of clonogenic cells in acute monocytic leukaemia.