Is there really an accelerated phase of chronic myeloid leukaemia at presentation?

Whether there is really a distinct accelerated phase (AP) at diagnosis in chronic myeloid leukaemia (CML) in the context of tyrosine kinase-inhibitor (TKI)-therapy is controversial. We studied 2122 consecutive subjects in chronic phase (CP, n = 1837) or AP (n = 285) at diagnosis classified according to the 2020 European LeukemiaNet (ELN) classification. AP subjects with increased basophils only had similar transformation-free survival (TFS) and survival compared with CP subjects classified as ELTS intermediate-risk. Those with increased blasts only had worse TFS but similar survival compared with CP subjects classified as ELTS high-risk. AP subjects with decreased platelets only had similar TFS but worse survival compared with subjects classified as ELTS high-risk. Proportions of CP and AP subjects meeting the 2020 ELN TKI-response milestones were similar. However, worse TFS at 3-month and survival at 6- or 12-month were only in AP subjects failing to meet ELN milestones. Findings were similar using the 2022 International Consensus Classification (ICC) criteria for AP replacing decreased platelets with additional cytogenetic abnormalities. Our data support the 2022 WHO classification of CML eliminating AP. We suggest adding a very high-risk cohort to the ELTS score including people with increased blasts or decreased platelets and dividing CML into 2 phases at diagnosis: CP and acute or blast phases.