Impact of the changes in chronic myeloid leukemia classification proposed by the 2022 World Health Organization: a single-center Brazilian study

INTRODUCTION: The latest edition of the 2022 World Health Organization (WHO) classification for chronic myeloid leukemia omitted the definition of accelerated phase. METHODS: This study evaluated the impact of using the updated classification in chronic myeloid leukemia patients treated upfront with imatinib by analyzing the outcomes of 139 newly diagnosed patients, previously classified according to the 2017 WHO criteria. RESULTS: Using the updated WHO Classification, eight (6%) cases previously characterized as accelerated phase were classified as chronic phase. Overall survival (OS) was comparable under both the 2017 and 2022 WHO classifications. For patients in the chronic phase, OS was 86% at 60 months and 70% at 96 months (compared to 85% and 69% respectively under 2022 criteria). Conversely, outcomes were significantly poorer for advanced stages, with 0% survival for the accelerated phase and 25% for blast crisis (p-value <0.0001). Progression-free survival was 85% and 69% for the chronic phase and 25% for blast crisis (p-value <0.0001) by the 2017 WHO classification and 83% and 68% for chronic phase and 25% for blast crisis (p-value <0.0001) according to the 2022 WHO classification. Independent predictors of overall survival included basophil count, 2022 WHO classification, and age at tyrosine kinase inhibitor therapy initiation. For progression-free survival, the 2022 WHO classification (specifically blast crisis) and age at diagnosis were identified as significant factors. CONCLUSIONS: Age, elevated basophil count, and advanced disease at diagnosis remain associated with worse outcomes. The omission of the accelerated phase did not significantly affect the prognosis in this cohort. However, it may affect the treatment of individual patients in Brazil, since higher doses of tyrosine kinase inhibitors are indicated for those who meet the criteria for the previous accelerated phase definition.