HR indicates hematologic response; CgR, cytogenetic response; MR, molecular response; BM, bone marrow; PBL, peripheral blood; C, complete; P, partial; M, major; N, no response; and UD, undetectable BCR-ABL transcript level.

Complete hematologic response: WBC count of less than 10 × 10⁹/L, platelet count of less than 450 × 10⁹/L, no immature cells (blasts, promyelocytes, or myelocytes) in the PB, and no signs/symptoms related to leukemia (including palpable splenomegaly). Complete cytogenetic response: 0% Ph-positive metaphases, based on results of conventional cytogenetic analysis. Partial cytogenetic response: 1% to 35% Ph-positive metaphases, based on results of conventional cytogenetic analysis. Major molecular response: BCR-ABL/ABL ratio less than 0.1% (international scale). Undetectable BCR-ABL transcript level: BCR-ABL/ABL less than 0.001% (international scale), corresponding to the lowest level of detectability of the method (10⁻⁴). Complete Molecular response: samples negative by RQ-PCR were analyzed by nested PCR and a complete molecular response was defined as nested PCR negativity.⁴⁸  Samples showing less than 1000 copies of ABL transcript were not considered evaluable and are not included in the analysis (range of ABL copies for CD34⁺ cells was 2998-30 792; range for CD34⁻ cells was 3425-18 693). The number of cells analyzed was (range) 118 000-860 000 and 130 000-1 100 000 for CD34⁺ and CD34⁻, respectively.