ABSTRACT
According to the World Health Organization (WHO) 21 AP is defined by any one of the following criteria: increasing spleen size, increasing WBC count or a platelet count > 1000 × 10 9 /l unresponsive to therapy, a platelet count <100 × 10 9 /l unrelated to therapy,
blast cells in blood or marrow 10 – 19 % , basophils in blood > 20 % , or clonal evolution (additional chromosome abnormalities in the Ph-positive clone). Currently, these recommendations are not universally used, and several recent reports on the treatment of CML have used different criteria, 20 that have been reviewed and adopted provisionally by an expert panel appointed by European LeukemiaNet, 18 namely a platelet count <100 × 10 9 /l unrelated to therapy, a blood or marrow blast cell percentage between 15 and 29, or a blood basophil percentage ≥ 20 ( Table 3.1 ). Table 3.1 also lists the criteria for the definition of BC, focusing on extramedullary leukemic involvement (such as lymph nodes, skin, bone, central nervous system (CNS), etc.) and on the blast cell percentage in marrow or blood, with an upper limit of 20 % for WHO and of 30 % for several recent reports. 18,20 Clearly, a shared definition of AP and BC is required. This was not critical until a few years ago, when treatment was ineffective and the prognosis was universally very poor; however, it may be critical today and may become even more critical tomorrow, following the introduction of imatinib mesylate, of second generation TKI, and other targeted agents, which may influence significantly response and survival. The next round of definitions will probably
include more use of cytogenetics, as well as new molecular data, with focus on point mutations in the BCR-ABL kinase domain and on gene profile.
