Which AML subsets benefit from leukemic cell priming during chemotherapy? Long-term analysis of the ALFA-9802 GM-CSF study

BACKGROUND: Priming with granulocytic hematopoietic growth factors may modulate cell cycle kinetics of leukemic cells and render them more susceptible to phase-specific chemotherapeutic agents. In a first report, we have shown that priming with granulocyte-macrophage colony-stimulating factor (GM-CSF) may enhance complete remission (CR) rate and event-free survival (EFS) in younger adults with acute myeloid leukemia (AML). METHODS: In this randomized trial, 259 patients with AML were randomized at baseline to receive or not receive GM-CSF concurrently with all cycles of chemotherapy. The effects of GM-CSF on survival were reported herein with a long-term follow-up and studied according to distinct biological subgroups defined on cytogenetics and molecular markers. RESULTS: The EFS rate was better in the GM-CSF group (43% vs 34%; P=.04). GM-CSF did not improve the outcome in patients from good risk subgroups, while patients from poor risk subgroups benefited from GM-CSF therapy. In this population, the difference in terms of EFS probability was mainly observed in patients with high initial white blood cell count and in those with FLT3-ITD or MLL rearrangement. When combining these 2 molecular abnormalities for comparison of the effect of GM-CSF priming, the difference in terms of EFS was highly significant (5-year EFS, 39% with GM-CSF vs 8% without GM-CSF; P=.007). CONCLUSIONS: Sensitization of leukemic cells and their progenitors by GM-CSF appears as a plausible strategy for improving the outcome of patients with newly diagnosed AML. Patients with poor-prognosis FLT3-ITD or MLL rearrangement might be a good target population to further investigate priming strategies.