Characteristics of accelerated disease in chronic myelogenous leukemia

Determination of the characteristics of accelerated disease in chronic myelogenous leukemia (CML) helps in individual prognostication, and in the introduction and analysis of investigative approaches based on risk‐benefit ratios. The outcome of 357 patients with Philadelphia chromosome‐positive CML was analysed from the time of development of suspected features of accelerated disease. Median survivals shorter than 18 months were associated with the appearance of any of the following: cytogenetic clonal evolution; extramedullary disease; peripheral blasts ⩾ 15%, peripheral blasts and promyelocytes ⩾ 30%, or peripheral basophils ⩾ 20%; platelet count < 1.0 × 10⁵/μl; marrow blasts ⩾ 15%, marrow blasts and promyelocytes ⩾ 30%, or marrow basophils ⩾ 20%. Relative hazard ratios, or risk of death per unit time, were calculated based on the relative survivals of patients who did or did not develop the particular feature of accelerated disease, after accounting for the time to development of the characteristic. Further analysis identified five features that have additive independent prognostic importance: cytogenetic clonal evolution; peripheral blasts ⩾ 15%; peripheral basophils ⩾ 20%; peripheral blasts and promyelocytes ⩾ 30%; and thrombocytopenia. By providing an objective estimate of prognosis in accelerated disease, the model identifies patients in need of different therapeutic interventions before the development of blastic crisis.