Subtype‐ and functional class‐dependent prognostic impact of CSF3R mutations in acute myeloid leukaemia: A cohort study of 2500 patients

Summary Colony‐stimulating factor 3 receptor ( CSF3R ) mutations occur in acute myeloid leukaemia (AML), but their prognostic significance remains unclear. We analysed 2500 patients with newly diagnosed de novo non‐acute promyelocytic leukaemia (APL) AML treated with intensive induction therapy. CSF3R mut were identified in 3.5% and frequently co‐occurred with CCAAT/enhancer‐binding protein alpha bZIP domain ( CEBPA‐bZip ) mutations and RUNX family transcription factor 1::RUNX1 partner transcriptional co‐repressor 1 ( RUNX1::RUNX1T1 ) fusions. In the entire cohort, CSF3R mut were associated with inferior relapse‐free survival (RFS), but not overall survival (OS) or event‐free survival (EFS). The prognostic impact was context‐dependent. The adverse association was most consistent in CEBPA‐bZip AML, with inferior OS, EFS (hazard ratio [HR], 2.76; p = 0.001) and RFS (HR, 2.66; p = 0.002) and persisted after multivariable adjustment and time‐dependent modelling of transplantation. Membrane‐proximal activating mutations (MPM) were associated primarily with inferior RFS (HR, 2.27; p = 0.001) in the overall cohort, whereas cytoplasmic‐tail truncating mutations (CTTM) showed no consistent adverse effect. In CEBPA‐bZip AML, both MPM and CTTM showed adverse EFS and RFS associations, although the CTTM subgroup was small. The prognostic impact of CSF3R mut in AML depends on molecular context and functional mutation class, with the strongest adverse associations observed in CEBPA‐bZi p AML.