The presence of cytogenetic clonal heterogeneity has been associated with poor prognosis in patients with acute myeloid leukemia (AML). Here, we reassessed this association. The study cohort consisted of all patients with an abnormal karyotype randomized in the EORTC/GIMEMA AML-10 and AML-12 trials. Abnormal karyotypes were classified as no subclones present (cytogenetic abnormality in a single clone), defined subclones present (presence of one to three subclones), and composite karyotypes (CP) (clonal heterogeneity not allowing enumeration of individual subclones). The main endpoints were overall survival (OS) and disease-free survival (DFS). Among 1291 patients with an abnormal karyotype, 1026 had no subclones, 226 at least 1 subclone, and 39 a CP. Patients with defined subclones had an OS similar to those with no subclones (hazard ratio (HR) 1.05, 95% confidence interval (CI) 0.88-1.26), but CP patients had a shorter OS (HR = 1.58, 95% CI 1.11-2.26). However, in a multivariate Cox model stratified by protocol and adjusted for age, cytogenetic risk group, secondary versus primary AML, and performance status, clonal heterogeneity lost its prognostic importance (HR = 1.10, 95% CI 0.91-1.32 for defined subclones versus no subclones; HR = 0.96, 95% CI 0.67-1.38 for CP versus no subclones). Also, the impact of having a donor on DFS was similar in the three clonal subgroups. In summary, in patients with cytogenetic abnormality, presence of subclones had no impact on OS. The dismal outcome in patients with a CP was explained by the known predictors of poor prognosis.
Keywords: AML; Clonal evolution; Clonal heterogeneity; Cytogenetic; Transplantation.