The emergence of ABL point mutations is the most frequent cause for imatinib resistance in chronic myelogenous leukemia (CML) patients and can occur during any phase of the disease; however, their clinical impact remains controversial. In this study, we retrospectively analyzed the predictive impact of 94 BCR-ABL kinase domain mutations (18 T315I, 26 P-loop, 50 in other sites) found in 89 imatinib-resistant CML patients. At imatinib onset, 64% of patients (57/89) were in chronic phase (CP), 24% (21/89) in accelerated phase (AP) and 12% (11/89) in blastic phase (BP). T315I and P-loop mutations were preferentially discovered in accelerated phase of BP CML, and other types of mutations in CP (P ¼ 0.003). With a median follow-up of 39.2 months (6.3-67.2), since imatinib initiation, overall survival (OS) was significantly worse for P-loop (28.3 months) and for T315I (12.6 months), and not reached for other mutations (P ¼ 0.0004). For CP only, multivariate analysis demonstrated a worse OS for P-loop mutations (P ¼ 0.014), and a worse progression-free survival (PFS) for T315I mutations (P ¼ 0.014). Therefore, P-loop and T315I mutations selectively impair the outcome of imatinib-resistant CML patients, in contrast to other mutations, which may benefit from dose escalation of imatinib, able to improve or stabilize disease response.

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In order to determine whether granulocyte colony-stimulating factor (G-CSF) alone initiated during steady state was able to mobilize peripheral blood stem cells (PBSC) in acute myeloid leukemia (AML) and to assess predictive factors for engraftment after autologous PBSC transplantation, we studied 49 successive adult AML patients for whom autologous transplantation was planned between July 1994 and November 1998. G-CSF was used as priming agent and was initiated at least 4 weeks after the last day of chemotherapy, while neutrophil count was >0.5 x 10(9)/l and platelet count was >30 x 10(9)/l. A median of three aphereses was performed resulting in a median collection of 14.8 x 10(8) nucleated cells/kg containing 7.7 x 10(8) mononuclear cells/kg, 47.1 x 10(4) CFU-GM/kg, and 3.8 x 10(6) CD34+ cells/kg. A significant correlation was observed between nucleated cell, mononuclear cell, and CFU-GM yields, while no correlation was found with CD34+ cell yield. Recruitment was not significantly different in patients with CD34+ leukemic cells at the time of initial diagnosis when compared to that of those presenting with CD34- blastic cells. Thirty-three patients actually underwent transplantation. Reasons for not autografting were inadequate stem cell harvest (ten patients), early relapse (two patients), prolonged neutropenia (one patient), organ failure (two patients), or patient refusal (one patient). Median time to achieve a neutrophil count greater than 0.5 x 10(9)/l and platelet count >50 x 10(9)/l untransfused was 13 and 36 days, respectively. A predictive factor for a shorter period neutropenia and a shorter thrombopenia was a higher count of harvested nucleated cells (p < 0.01 and p = 0.02, respectively). A higher count of harvested cells was also a predictive factor for less red cell and platelet transfusions (p=0.03 and p=0.02, respectively). The number of CD34+ harvested PBSC was not predictive for engraftment. We conclude that PBSC mobilization with G-CSF alone initiated in steady state is a feasible, safe, and suitable procedure for harvesting cells in sight of autologous transplantation in adult acute myeloid leukemia.