Untreated, CML undergoes 3 phases: Chronic phase: An initial indolent period that may last 5 to 6 years Accelerated phase: Treatment failure, worsening anemia, progressive thrombocytopenia or thrombocytosis, persistent or worsening splenomegaly, clonal evolution, increasing blood basophils, and increasing marrow or blood blasts (up to 19%) Blast phase: Accumulation of blasts in extramedullary sites (eg, bone, central nervous system, lymph nodes, skin); blasts in blood or marrow increase to ≥ 20% The blast phase leads to fulminant complications resembling those of acute leukemia, including sepsis and bleeding.