Imatinib Mesylate Therapy in Late Ph+ Chronic Myeloid Leukemia Patients in Stable Complete Cytogenetic Response after Interferon-Alpha Results in a Very High Complete Molecular Response Rate.

Imatinib mesylate was given to 26 Philadelphia positive (Ph+) chronic myeloid leukemia (CML) patients who were in late chronic phase (CP) and in stable complete cytogenetic response (CCR) after interferon-alfa (IFN-α), but showed persistent positive residual disease at PCR analysis under this treatment. At diagnosis median age was 40 years (range 21–64) and according to Sokal's score, 18 patients were low risk and 8 were intermediate risk. Median IFN treatment was 88 mo.s (range 15–202) and median CCR duration was 73 mo.s (range 10–148). Imatinib was administered at the standard dose of 400 mg/die, after stopping IFN for 1 week. Residual disease was measured on bone marrow (BM) cells at baseline, before starting Imatinib, at 3, 6, 12, 18 mo.s and at the last follow-up (median 32 mo.s, range 21–49), by assaying BCR-ABL transcripts using quantitative PCR (RQ-PCR). The copy number (CN) of BCR/ABL and ABL transcript were derived by the interpolation of CT values to the appropriate standard curve, and the result, for each sample, was expressed as ratio of BCR/ABL mRNA copies to ABL mRNA x 100 (normalized copy number - NCN).